COBBA and V2578 got difference?

[hooi76]

Hi everbody, I need your help on this COBBA and V2578 or V2758 (not very sure), is there any difference. Coz i tried to change the COBBA to a V2578 or (V2758) and the phone shows contact service! (although i update FAid and SP and change IMEI), but when i change to COBBA back, the phone is back to normal again.

Is it true?