To unlock a Nokia 5310 from T-Mobile it is completely free and only takes a few steps. Your Nokia 5310 will first need an unlock code. As stated in this article, you can get yourself a free unlock code by calling the T-Mobile support line at 1-800-866-2453. In exchange for the unlock code, they will request your Nokia 5310′s IMEI number, which you can find by typing *#06# and hitting enter. Unfortunately, many of the Nokia unlock code generators do not have codes supporting the Nokia 5310, so you are probably best off calling the T-Mobile. Once you have your free unlock code for your Nokia 5310 you can begin the unlocking process. Here are the steps to unlock your phone for free:
How To Unlock Nokia 5310
1. Type #PW+
2. Enter your unlock code (Warning: Entering 3 or more incorrect unlock codes may auto lock your phone!)
3. Now type +1#
4. Your Nokia 5310 phone should say “SIM Restriction Off”
You can find the original steps to this guide from these articles: How To Unlock A Nokia Phone. If you are having problems or have some more information, please comment or leave a question below. Thanks and God bless!