MTN non service with account

Good day. I have had my mtn account since cell phones were introduced. This month an amount of R610.33 was debited to my bank account. When I phoned mtn I was put through from pillar to post. Eventually the problem was sorted and I was told to contact my bank to have the debit order reversed which I did. Now my service has been cut because they say I owe them the amount mentioned. My phone number is *** and the ref no given to me is ***. I cannot phone them because my service has been suspended and I can't get through on another phone because the option given " does not exist". Please help me as no one else is Thanks Veronica Campbell