Bad treatment

I made a very biggest mistake of my entire life, I took a Data contract with CELLC and everything went well for sometime and CellC offered me a cellphone contract and since I was on the market for a new cellphone I took the deal. We started well till I experienced problems on my FNB account that lead me to changing banks and I went from FNB to Nedbank. I updated CELLC about this matter and things were good until in December where CellC sent their debit order earlier than expected without communication and then everything fell apart because in December I got paid on the 31/12/2019 not on the 13th as per CELLC psychic thinking without contacting account holder. Then in January CellC went on to debit my account 3 if not 4 installments without communicating with me whatsoever. I did not like being treat the way CellC did and I reversed the amount hoping to hear from them but that did not help because CellC just handed me over to their collections company and this affected my credit score negatively that my bond application is hanging on a single thread. My balance at CellC is R13345 which I am willing to settle just to clear my credit record. After I pay this amount I demand a paid up letter and a cancellation of my data contract asap