[Q] network and signal problem after installing rom from sammobile

hi all,
i bought samsung trend duos gt-s7562 FROM CHINA with following device information(I m from Pakistan)

baseband:S7562ZCMH1
KERNELI DONT REMEMBER AS IT HAS CHANGED AFTER FLASHING ROM(PAKISTAN) FROM sammobile)
build no: S7562ZCAMH1

now i m having signal an network problem. it says SIM CARD REMOVED
Wi-Fi working properly but some apps crash even dont bother to start at all

device current information
baseband: S7562ZCMH1(is this the culprit)
kerenl: 3.0.8- 1260195 dpi@dell167#1 tue oct 8 16:31:20 kst 2013
build no: s7562XXBMJ1

Do i have to update the baseband also? if yes then where to download and how to flash
if i want to insatll any custom rom then how to flash recommended baseband

thanks to all (this is all i know about android)