Accidently losing your mobile phone address book is one of the biggest fears of many mobile phone users. Most don't know their mobile phone contacts by heart and don't have the information stored elsewhere. T-Mobile USA, like many of the major mobile service providers, offers its customers a way to upload the address book on their mobile phones to an online database. This makes it easier to restore accidentally deleted contacts to your phone or transfer contacts to a new handset. The service is called Mobile Backup and is available only on certain T-Mobile phones.
Verify that your mobile phone is compatible with T-Mobile's Mobile Backup system.
Go to the T-Mobile USA website on your computer's web browser. Log on to the My T-Mobile site. Click "Contacts" under the Connect with MobileLife heading to the right of the My T-Mobile homepage.
Open the address book management feature. Click "Synchronize Now." Verify that the contents of your address book are now the same in both your online Mobile Backup account and your mobile phone.