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BYO phones: How to take your phone to another carrier and save money

Taking your phone between networks in the US can be a tricky business, but well worth it. If you’ve got a handset that you’re still happy with, but want to ditch your current carrier, keeping your old device instead of buying a new smartphone on a contract can result in huge savings.

We’ve been championing the benefits of a BYOD cellphone plan for a while now, but the problem is that the carriers themselves aren’t making it easy for customers to take their handsets to a rival’s network. Differing technologies and phone-unlocking policies mean it can be confusing determining if your smartphone will work on a different network.

Read below to find out more about wireless networks, or skip ahead to your carrier: Verizon. AT&T , T-Mobile , or Sprint.

Verizon and Sprint use CDMA technology; AT&T and T-Mobile use GSM.

These two standards are not compatible

CDMA vs. GSM: a quick overview

The first hurdle when moving between networks is a big one; US carriers don’t all run on the same kind of cellular technology. If your current carrier is set up for one, and your desired carrier set up for another, then it's likely you won't be able to use your current phone on the new network.

Cell phone companies operate under one of two types of networks; either CDMA or GSM. Of the four biggest US carriers, AT&T and T-Mobile run on 'GSM' networks, while Sprint and Verizon Wireless use 'CDMA'.

GSM phones use a SIM card for 2G (voice and text), 3G (voice, text and internet), and 4G (high speed internet and VoLTE) operation. This is a small removable plastic card that stores the data needed to identify a subscriber on a wireless network.

The phone itself is not part of the authentication process; the SIM card handles all of that.

This is great news; you can remove the SIM from your current phone and insert it into another compatible device, provided it’s either with the same carrier or you’ve ‘unlocked’ it from its original network for use on another. Swapping the SIM means the new phone will operate over the same network with the same phone number.

GSM is common globally, and is used in far more countries than CDMA.

Phones running on CDMA networks do not use a SIM card for 2G or 3G, but do still require one for 4G. Electronic serial numbers are used to identify subscribers for 2G and 3G. These serial numbers are coded in to the phones themselves, which creates a problem.

You will need to get your new provider to grant permission for your device to be given a serial number (and thus a working service line and phone number) on its network. This permission is not often granted.

CDMA is not nearly as common as GSM in global terms. Travelling with a CDMA phone may be difficult.

A few phones, like the 'CDMA' variants of the iPhone 6 and 6 Plus, are designed to work over both CDMA and GSM. These are often referred to as ' global' by carriers. If you're lucky enough to have a phone like this, you may be able to move to most carriers.

Unlocking your phone

Device-locking is common practice in the United States. This is when a carrier places a block within the phone to restrict it from working on any network but its own.

Getting your phone unlocked can range from trivial to downright tricky, depending on your carrier. Each handles the process in its own way, which we'll cover in each section. If you've finished your contract, paid for your phone in full, or have used it for over one year on a prepaid service, then chances are you're eligible for unlocking.

If you bought your phone off-contract (i.e. an iPhone directly from Apple for full outright price), then it should already be unlocked.

Verizon phones

  • CDMA carrier
  • Phones will not work on Sprint
  • Verizon will not accept Sprint phones on to its network
  • Phones cannot work on AT&T or T-Mobile networks (unless global)
  • Some phones may be compatible with Verizon MVNOs
  • 3G: 850MHz, 1900MHz
  • 4G LTE: 700MHz (band 13), 1700MHz (band 4), 1900MHz, (band 2), 2100MHz (band 4)

Verizon is a CDMA carrier, so taking your Verizon device to another network (Sprint) isn’t at all easy. As mentioned above, CDMA devices require permission from a network to gain access. The two biggest players - Sprint and Verizon - do not grant each other's phones this permission.

You might have luck with a Verizon MVNO like IQ Cellular or Net10. To be sure, run your device’s ID number through their websites to determine eligibility.

According to Verizon’s website . most post-paid devices sold through its own channels are unlocked from the start. This holds true for both post-paid and prepaid phones.

Prepaid 'Phone-in-the-Box' devices are locked to Verizon's prepaid services for six months, and to the Verizon Wireless network at large for 12 months in total.

To obtain an unlocking code, you may call Verizon on (888) 294-6804.

AT&T phones

  • GSM carrier
  • Phones should be compatible with T-Mobile Network
  • Phones can't be used on Sprint and Verizon networks (unless global)
  • 2G: 850MHz and 1900MHz frequencies
  • 3G: 850MHz and 1900MHz frequencies
  • 4G (LTE): 700Mhz (bands 17 and 29), 850MHz (band 5), 1700 MHz (band 4), 1900MHz (band 2) and 2100MHz (band 4)

AT&T uses a GSM network, meaning its phones all come with a SIM card. In theory, you should be

able to take your AT&T-branded device to fellow GSM network T-Mobile. For the most part this holds true, although there is the odd exception - so be mindful.

Note that T-Mobile and AT&T operate over different frequencies. Some of them overlap, but not all. This means that, while your phone may ‘work’ when going from one to another, you may suffer diminished reception, as your device may not be compatible with all the frequencies utilized by whichever network you have switched to.

Phones sold through AT&T are locked to its network. You can request an unlock code, but you need to fit the criteria:

  • It must be paid off in full, and not still on contract or a payment plan
  • It is not currently active on a different AT&T customer’s account
  • If you performed an early-upgrade, you must wait a 14 day ‘buyer’s remorse period’ before you can request an unlock to your previous device
  • It must not be associated with fraudulent activity, reported lost, or reported stolen
  • Post-paid customers must have an account that has been active for at least 60 days, with no past due or unpaid balance
  • Prepaid devices must have been active for at least six months of paid service

AT&T reserves the right to amend this unlocking policy at any time without advance notice.

T-Mobile phones

  • GSM carrier
  • Phones should be compatible with AT&T
  • Phones can't work on Verizon, Sprint, or any CDMA network (unless global)
  • 2G: 1900MHz
  • 3G: 1700MHz, 1900MHz, 2100MHz
  • 4G LTE: 700MHz (band 12), 1700MHz (band 4), 1900MHz (band 2), 2100MHz (band 4)

T-Mobile is a GSM carrier, so its devices rely on SIM cards for voice, text and internet services. Once your phone is unlocked, moving to another GSM network is as easy as getting a new SIM and using it to replace your old one. Just make sure that the new network uses mobile frequencies for which your phone is designed.

T-Mobile’s and AT&T’s networks have many overlapping frequencies, so moving between them should be relatively simple. There’s a small chance you may experience diminished reception if your phone only works on some, but not all, of the new network’s frequencies, but this is generally unlikely for anything other than 4G LTE.

T-Mobile devices are often locked to its network. Unlocking is free and is handled within two business days, but your device must meet the eligibility criteria.

  • It must have been active for at least 40 days on the T-Mobile network on the requesting line
  • If the device was financed through T-Mobile’s Equipment Installment Plan (EIP), then you must have paid off the full owed amount before the phone can be unlocked
  • If the devices is on an account that is under a service contract term, then at least 18 consecutive monthly payments must have been made, or the account must have been migrated to a Simple Choice no-contract plan
  • If associated with a cancelled account, the balance owing must be zero
  • It must have been active on the T-Mobile network for more than 12 months
  • If under 12 months, the associated prepaid account must have had more than $25 in refills for basic phones or $100 in refills for smartphones/tablets since first use date

You can contact T-Mobile customer service to request your unlock

Sprint phones

  • CDMA carrier
  • Phones will not work on Verizon
  • Sprint will not accept Verizon phones on its network
  • Cannot work on AT&T or T-Mobile networks (unless global)
  • Allows devices to be used on selected Sprint resellers such as Ting
  • 3G: 800MHz, 1900MHz
  • 4G LTE: 800MHz (band 26), 1900MHz (band 25), 2500MHz (band 41)

Sprint is a CDMA carrier, so any device brought to its network must not only be unlocked, but must also be authorized by Sprint. Currently, Sprint will not accept Verizon phones. You will also not be able to take a Sprint phone to the Verizon network.

It’s not all bad news. Recently, Sprint launched a ‘Bring Your Own Device’ campaign for selected MVNOs (smaller wireless providers who operate on its network).

This means that some (not all) Sprint devices will be able to be used on either Ting or Boost Mobile (unfortunately, Sprint’s prepaid MVNO, Virgin Mobile, doesn’t accept phones from any other carrier – you’ll have to buy a Virgin Mobile handset to sign up for service).

As for going to AT&T or T-Mobile, some handsets sold by Sprint are marked as ‘global’ phones (meaning they also have room for a SIM card, despite running on Sprint’s CDMA network), and have dual CDMA/GSM capability. In general, though, most phones don’t have this ability and can’t make the transfer.

Even if you do get the all-clear, getting your phone unlocked is the tricky part. While Sprint are happy to unlock phones for international use (provided the device is paid off, and the customer’s account is in good standing), the company isn’t as enthusiastic about unlocking devices when customers wish to take them to another carrier. There’s more info about the unlocking process – and what a headache it can be – here.

Want to unlock your phone?

Thanks to changes in FCC regulations, it is now really easy to network unlock your phone. Follow the links below to learn about how the different rules and procedures for the network you're currently on. If you have unlocked your phone already, check out our picks for the best plans for your device.

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