I have a gsm pre unlocked via rebel sim. I start my phone and it's automatically on roaming when i try to sign in with a username and password i get a "sign in fail" and i get this message "This may be due to low network coverage or the phone settings on your sim card need to be entered manually". I have no idea what this means or what to do from here. When i click on change the phone settings option i get asked from 3 things. 1. Internet apn, 2. Username, 3. password... Can anyone please help me out with this.