Pathetic service from Cell C

I've got two contracts with Cell c in June I changed my banking details, whoever assisted me only changed the debit order details on one contract. End of June I had to do an EFT payment, end of July my banking details were still not updated. End of August cell c double debited my account for July & August. Beginning Sept my account was suspended saying they did not receive payment for August. I've sent through proof of payment to several email addresses with no response. End September Cellc debited my account for 3months payments, when I call to ask for a refund I'm told it takes 7 working days and that my account is with the Finance Department. I've received several reference numbers but no one is coming back with any resolution around my request for a refund. This is pathetic service