Cell C woes

Having had a successful relationship with Cell C for many years, I was dismayed that when I changed debit instructions the wheels literally fell off. It appears that when Cell C captured my new details they erroneously failed to capture the expiry date on the "new" credit card. Subsequently they forced my old (now closed) account open and took money from same which placed me in overdraft/cost me a pile of bank charges and then promptly cut my service, despite my making repeated trips to Cell C and confirming that they did indeed have the correct expiry date on their system. I am now being bul**** with the threat of legal action when I have done nothing wrong and have had my service cut. I have both visited their stores (5 times), contacted them telephonically on numerous occasions, and sent them repeated emails all to no avail. The only responses I get are pre recorded messages saying I owe them money. Their service has been terrible and I would not recommend them to anybody, as they appear to be a faceless company that is either unwilling or unable to address the valid complaints of their (previously) loyal customers.