Appalling service and disgruntled customer

After all the proof I have given to cell c that they had given me 3mnths free for my WiFi that they have installed onto my property. Today I still get calls from them saying I owe them. It is exhausting and not pleasant every time I have to tell the consultants that are calling me that I do not owe cell c. I'm really tired of the way cell c is treating me as a customer. The poor service I'm receivin from cell c is appalling. I'm not sure if I want to keep their services any longer because they have proven to me that they do not do their job and they have empty promises. I've never been soo unhappy and full of regrets on why I took up WiFi with them and also they still keep calling my surname wrong because their data captures captured it as something else I also wrote several e mails to them to correct the surname up to date it's still not corrected.