my blackberry bold 9650 cant mke calls

hey guys am a newbie on this forum but i have been following what happens here and you guys do a great job.thumbs up..i successfully unlocked my sprint blackberry bold 9650 to mtn zambia but i cant send or receive texts.i can only receive calls but cannot make calls. i cant even check my available credit, i tried changing the settings to gsm and 2g.but all that was in vain.please guys any form of assistance will be appreciated.i know this thread is long but i need your help. thanks in advance