How do you change your phone number with t-mobile?

A few weeks ago, I lost my phone which was a prepaid service in t-mobile and now that I have a new phone, I want to use the same phone number that I had in the last phone but on a different/new phone. Is there anyway that I can change my new phone number and transfer the old number to the new phone? Is there a fee? I am also still using the t-mobile prepaid service as well. That way, the lost phone will be useless and I can still use the old number for the new phone!|||Your going to have to go to a T-mobile store. Just T-mobile, not an authorized dealer. They will give you a new sim card, which they may or not charge you for ($20), and they will call T-mobile pre-paid customer care to update your sim. You definitly need to get a new sim before you call any 1800 numbers. Plus t-mobile employees are more than happy to do this for you in the store. Saves you the aggrevation of finding imei numbers and sim card hooplah!|||Just call 1-877-778-2106 to activate the new phone %26amp; SIM on your old number, there%26#039;s no fee to do this with T-Mobile Prepaid. Did you call to report the old phone lost and suspend your balance? If you still had a balance on the old phone when you reported it lost, you%26#039;ll be able to get it back.