Penalty for upgrading

In December I whent to Telkom Benoni office to upgrade from 3GB to 20 GB when my debit order went off. Telkom took R1578 instead of R400 when I phoned them in January to finds out why? I was told they gave me a penalty but do not understand why? They will follow up with the billing department ,and they will phone me back. No one phoned me back so I went to the bank to reverse the debit order and only Pay R480 on this acount. They have disconnected my service on the 19 February I went back to telkom office in Benoni I was told they cannot do anything they will send an e-mail through to billing department reference number (***0) And billing dept ref number (***6). All I need is an explanation as to why there was a penalty and why my service has been suspended. I am studying and require my network to be sorted out ASAP.