Android : Android smart phone is broken by rom

I have a spanish smartphone (monte Carló - skate orange). Someone installed a custom ROM. Now the base de bandera is disconected. I guess the base de bandera is the bandwidth the phone uses for calls. Now i cant make calls and cant run in recovery mode.

I think if theres no easy solución i should wipe the phone and reinstall the factory OS (android 2.3 gingerbread).

Any advice on how. Im a linux based web programmer who know very little about mobiles