Terrible service from Summer Mobile

In April of this year I was contacted by Summer Mobile to renew my MTN contract. I informed that that I would like to renew it without a device. At the end of June I noticed that my bill was higher than my previous bill, not lower so I called MTN who informed me that I must deal with Summer Mobile directly.

I called and spoke to Kate who assured me that she would look into my query and get me to me. She didn't. I then called and spoke to Connie who said she would ask the courier company if they had delivered a new device to me (they hadn't), and once they had confirmed she or Kate would get back me. They didn't

I then called again and spoke to Sara, who said that they hadn't received any feedback but she would follow up and get Kate to call me back by the end of business that day (30/7/2018). She didn't

I called again today and spoke to John. He informed me that my contact has been cancelled as of 5/7/2018 and my current amount payable should be R 249, not the R 937 that I have been paying. I then asked him why MTN have billed me R 937 in on 25 July and he advised that this was a billing issue and I must talk to MTN again. This is unacceptable.

I then asked to speak to the manager who was unavailable and then to a person higher up who could help me. I was told to call back to reception and ask for Samantha. I called twice at about 12.30 but there was no receptionist there to transfer my call.

I would like an immediate resolution of my query and to be informed on how the money that I have been overpaying since April will be returned to me. Please contact me urgently.