Unco-operative accounts department

The accounts department are totally ridiculous. I asked that they do not bother my brother but send the account to me so they send to him regardless and I ask them repeatedly. Eventually they send a balalnce statement which does not tally with what the medical aid said the co payment would be. I ask for a full invoice/detailed transactions and still do not received it however I get a threatening sms that I had not paid in 30 days. Send the account then it will be paid on return if all is correct.