Supersonic

I had a subscription with Supersonic in 2021. In April 2021 we got fibre in our area and Supersonic at the time could not assist with fibre connection. I sent an email to Supersonic with a 30 day notice of cancellation of my subscription. I never got any further correspondence or account from them to date. On the 05 March 2024 I received an email from a credit solution company (Nimble Credit Solution) that I now owe Supersonic R798,00 (2 x R399). I queried the said amount and was sent a statement and my email with a modified date of 14/05/2021 stating that account was billed for the month of July which will be credited to my account. Last payment from me to Supersonic was 01 April 2021. I paid R399,00 on 08 March 2024 as that was one month payment stating that one month will be credited to my account. However, the credit company requested a further R452,27 from me now. Amount handed over to them was R798,00. I am extremely upset. I always pay my accounts well in advance. If this amount was requested in 2021, I would have paid it then. Now there is a R7,38 interest and R45,89 fee suddenly added. However initial amount was just the 2 x R399 = R798. Just to get this sorted, and avoid a negative credit listing on my profile, I paid a further R399 today but refuse to pay the additional charges. I feel that it is Supersonics mistake almost 3 years ago and now I have to pay for Supersonics incompetence. I will definitely NOT recommend Supersonic to any one and will definitely NOT be doing any business with them ever again.