Two things:

1. All the sites that write about ROMs have go back instructions. These instructions are often technical and not the same for each phone.

The most common go back for a blown phone is to take it to the service counter and have them re-flash your phone.

2. Some phones must be setup with APN entries. This is network/carrier dependent and you'll use their settings. I can't know this but have googled it many times then punched in the settings on dozens of phones. The irksome thing here is across a dozen phones it's not exactly the same steps.