Urgent help with samsung

homealone_2

my basic samsung phone is being used in thailand by a maember of my family as she had no phone. it has been costing her £15 a day sending text to work and kids and so someone suggested she buy a local sim. she went to a 711 store and for some reason it would not accept it. anyhow problem is since then she is unable to read any messages that she receives or sends. it beeps in normal way and right at top of screen she can see name and first few words of message but nothing else. not even when she goes to the persons page the message although told her was sent is nowhere. she is panicking as her son stayed out all night and she in bits trying to figure a way of contacting him. when she calls she cant hear him properly and she runs out of credit before she gets anywhere she has took sim out gave clean and put back but no difference can someone tell me what could be wrong so i can pass this on via her hotel phone