Default [Q] Verizon Galaxy s3 connection problem or invalid MMI code

Hi
I am a newby and i had a verizon galaxy s3 and i sent it to my sister which leaves in the Dominican Republic, verizon told me that the phone was unlocked so when she putted it the sim card messages and calls works fine but when she tries to check her balance or tries use any of the UUSD codes that the provider use over there she gets this message CONNECTION PROBLEM INVALID MMI CODE any help would be appreciated it
thanks

running stock android 4.3 jelly bean