Calls suspended

My daughter received a sms stating that her account (which I am paying) is overdue. I sent her all the proof of payments showing that the account is not overdue. She emailed mtn and called the centre several times without success. It seems as if mtn is run by robots. She was unable to connect to a human. She has not received any replies. I don't know where to send the proof of payments or what number to call to speak to a person. mtn is as pathetic as most other service providers.