On Air dispute

Wish to refer to a previous review from this company. I feel I'm being harassed for payment from their billing department. No communication between billing or accounts department. I'm waiting on proof of recording that I signed for 24 month contract. To my knowledge it was 18months. I sent my proof of payments to them. They claimed I had a credit of R480,00 on the one account and debit of R480. Which should have canceled my debit according to my records but they insisting that I signed up for this 24month contract. I received an email from their accounts that the one account has been settled in December 2021. What I don't understand if I signed if it was supposed to have been a 24month contract why did receive an email from them stating I have settled my accounts. I opened the account in June 2020 of September 2021 I should have been a settled with both decoders of R320. I made payments up to December 2021 which I should not have done. This company debits you without your permission and says it will benefit you in the long run. I'm high fed up.