Account locked without any notice

I have a contract with MTN , the account number is A*** and it was linked to another contract I have with them. The one is a wireless router and the other a mobile phone . I never received invoices for the phone . I had switched banks so the payments didn't go through as usually so without my knowledge I was sent to the legal team . They told me the amount that I was behind on . I payed the amount and sent a fax as was requested by them to prove my payment was done and also to cancel the mobile device as I no longer even had it . It has been weeks and my account still hasn't been fixed and whenever i try to call 808 I can't reach the legal team and they ask me to leave a message which they never respond to . I can't receive any help from the stores as they can