Bad telecoms experience with Cell C

I had once had a contract with Cell C which they are now refusing to let go off peacefully I always made payments via eft and paid more than the agreed amount and 10 days prior to the initial agreed date and would send proof of payments and they would still attempt to go and debit then charge me penalties now my credit record is damaged because Cell C wants to make me pay for their incompetence

When I ask them why they sent me to lawyers I was first Told it’s because of a data sim I had taken with them back in 2020 when their salesperson told me the data sim isn’t a contract of which I only used for two months and paid for that two months than cancelled 30 days prior like I was told I’ve sent every proof of payment I’ve made for the year 2021/2022 but they refuse to back date the payments and clear the mistake on their side my contract came to an end feb 2023 and I’ve been struggling With them rectifying their mistake since and the amount keeps going higher and higher mind u this problem started when they started missing debit order dates and would still charge me penalty fees for failed debt order than I made arrangements and was told I needed to pay 5 days prior if I am going to make my Own payments I paid 10 days prior but still