The honest answer is to go through your cell phone company.  If you have a phone using a SIM card, you can contact your carrier for help.  T-Mobile and AT&T both provide cell phone unlocking services for their customers after a few months into their contracts.  The main reason you will want to go through your cell phone provider to get your mobile phone unlocked is to spare yourself from a breach-of-contract that other methods may cause.  When you originally signed up with your cell phone carrier, you agreed to follow their rules.  Sometimes their rules strictly prohibit tampering with your cell phone, especially if it’s not your property.  Many times when you sign a contract, if you got your new phone for free or for a very low price, you don’t actually own your cell phone.  Basically what happens is you’re “renting” it from the carrier while you’re still under your 2 years of service.

If you aren’t under the “renting” category of cell phone users, you’re free to choose whatever unlocking option you want.  However, through my experience, the best method for unlocking your phone is through the carrier.  If you don’t have the choice available to you, have a local third-party business do it for you.  While it costs more than using a simple website, you’re much more likely to have a working phone.  When you unlock your phone yourself, you’re able to permanently disable service to the phone if you do the wrong thing.

If you’ve come upon a stolen phone, there’s no way you can get it unlocked.  Once a phone is reported lost or stolen, it’s impossible to get it to work with a carrier.  No website or person will be able to legally unlock the phone.

Under T-Mobile’s terms of service, you can have your phone unlocked after having your account open for 90 days.  Once having a phone unlocked during this period, you have to wait another 90 days until you can have another phone unlocked.  T-Mobile also will only give unlock codes to original T-Mobile phones.

If you have had your T-Mobile plan for 90 days, you can call them to request an unlock.  When you call their customer service number, tell them you need to have your phone unlocked.  If they ask you why, tell them you need it unlocked because you’re going overseas (don’t tell them you’re unlocking the phone to use with AT&T or another carrier).  While they probably won’t do anything because you told them you were switching carriers, there’s always a chance a “hidden fee” may pop up so avoid it with the overseas excuse.

The T-Mobile representative should happily give you the information you need to unlock your phone (assuming you said and are doing the right things).  Hopefully this will be as far as you need to for getting your phone unlocked.

If, for whatever reason, you aren’t able to get T-Mobile’s customer service to take care of you, there are other ways to get your phone unlocked.  One way is using a website or business to unlock your phone for you.  Many websites sell or provide software that decipher the codes from your phone and generate the secret unlock code.   Each unlock code is unique to the phone so you have to be careful what you type in.  Local businesses or cell phone stores sometimes provide T-Mobile unlocking services too.  They often charge around $15 to $30 to unlock your phone but often can do it without you having to worry about having your cell phone damaged.  So, besides using T-Mobile’s customer service, my most recommended option is to use a local business to unlock your mobile phone.