Cell C - Absolutely shocking service and been overcharged

To cut a long story short. Cell C has been over charging me as they were charging me for a hand set which I did not have. End Dec 19 they agreed to reimburse me approximately R7800. they then came back and said they would credit my account, which I did not want as I wanted the cash. Now they are saying that "apologies that we have not charged you for a handset, however on your next invoice we will be charging you going forward. ***? almost every 2/3 days I have had to follow up with them even though they said they would get back to me. I have spoken to team leaders who say it has been escalated and I spoke to Busisiwe Mange (team leader) (I picked up another Hello Peter complaint about Busisiwe about broken promises) who then apologised and ....... we are so sorry, blah, blah, blah and I will get back to you by Monday 27 Jan 20. well obviously they didn't get back to me. I experienced this with quite a few other Cell C staff. Busisiwe even gave me her email and I emailed her only to receive an incorrect email address, even though it is exactly as she gave it to me. It is absolutely shocking to have to experience such poor service. I must have called about 8/10 times; each time spending a long time on the phone. I do not know what it will take to sort this out