Can I use a used iPhone with my carrier?

If you've recently bought a used iPhone and want to get it going on your carrier, there are a few things you'll have to consider beforehand.

• Buying locked
• Buying unlocked
• Is it compatible with your network?
• The bottom line

Buying a locked iPhone

This is the first step in checking if your used iPhone will work with your carrier. Ask the seller which carrier they were using the iPhone with. If they were using the carrier that you want to use, then you're good to go. If they refuse to tell you, then that should send up a red flag and you probably shouldn't buy the iPhone.

Buying unlocked

If you want to use your used iPhone on a carrier other than the one it was used with before, then you'll need to check if it's unlocked.

It's best to buy an unlocked phone in the first place, but just in case, the best way to check is as easy as inserting a SIM card. Here's how to run the SIM unlock test on a used iPhone:

1. Ask the seller what carrier their iPhone currently works on (let's say AT&T).
2. Borrow a SIM from a friend on a different Network (eg. Verizon). If you're really smooth, you might even be able to borrow one from a carrier's store.
3. Make a call on the "unlocked" iPhone with the owner's SIM to make sure the phone works.
4. Power off the phone.
5. Swap in the other carrier's SIM and try and make a call. If it connects, the phone is unlocked!

Is it compatible with your network?

iPhones connect to mobile networks via radio signals, also know as "bands." Certain carriers will use certain bands, meaning not all phones are compatible with all carriers. Not only that, but certain networks use different connection technologies, which makes compatibility even trickier.

Luckily, iPhones are some of the most widely compatible phones in the world; you'll just have to make sure that the iPhone model you bought works with your carrier. The model number appears on the back of your iPhone, under the word "iPhone."

Note: Though your used iPhone may be compatible with a certain network, you may not receive total coverage in all areas nor may you receive full LTE speeds everywhere you go.

All iPhone models are compatible with AT&T's network.

All iPhone models will work on T-Mobile's network; however, some models may only be able to receive 2G speeds. You'll need to double-check with T-Mobile directly to confirm whether or not you will be able to receive 3G or LTE in your area. You can call T-Mobile's customer service line at 1-888-795-3776.

Verizon is the most difficult carrier to deal with when it comes to unlocked phones. If you bought a used and unlocked iPhone, Verizon will first have to decide to allow you to bring it to its network. With any iPhone newer than the iPhone 5, your phone should work with Verizon, but whether or not they let you in is a different story altogether.

Your best bet is to call Verizon's customer service line at 1-800-922-0204.

Most iPhone models will work on Sprint's network, but you will have to call them first to see if you'll be able to receive 3G or LTE data. Some model numbers of particular iPhone versions may not work with Sprint, due to network restrictions.

In some cases, Sprint may deem an iPhone ineligible, though the only way to find out any of this is to talk to Sprint directly.

You can head into the nearest Sprint store or you can call their customer service line at 1-866-789-8292.

The bottom line

In terms of model, newer iPhone models have a better chance of working with the carrier of your choice. Make sure it's unlocked or at least locked to the carrier you want to use. Don't bother with Verizon is if it unlocked.