Invoiced incorrectly because I wanted to cancel my account

Good day

I have two services from Supersonic an LTE and a fibre line which cost a R1000 a month in total. I requested to cancel my fibre account with Supersonic mid Feb 2021 via email. I got an automatic reply and that was it. March came it was still connect and I paid the account as per normal April came and I was still connect with no response from the cancellation team. I called customer service once again and the person said it still was not cancelled and he assisted me by requesting the cancellation again. End of April the line was still not cancelled because of this I could not get a new Isp to connect me. I called customer service once again and they told me, my fibre account is cancelled but the line is not released. I have to settle my bill, I checked my bill which now had an amount of R887.96 overdue which I could not understand. Because I paid the R599 for the LTE in April just not the fibre as it was supposed to be disconnect, so I was expecting an overdue amount of R395. When I queried this they said there was an error and my account would be credited. Today I asked again as to when will I receive the corrected invoice in order to settle the bill. I got an invoice of R13 something thousand and Supersonic said I have not made one payment on my account. I have my internet banking statements as proof that I paid it every month and my Feb bill before I informed them that I wanted to cancel had an amount outstanding of R98.53. So honestly I am extremely frustrated with this Isp as you are not allowed to speak to the Supervisor, Manager, cancellation dept or Billing except for billing customer service. It has cost me a lot of airtime dealing with them with no success. I would not recommend this company to anyone.

Kind Regards Ebrahiem Adams