*****ulant contract issued by Cell C

Please help! Problems with Cell C for few months already. Was telephonicaly contacted by Cell C employee, offered me new contract for R99, more for less, as my old contract was due to expire 28 Sept. 2023. At first, I refused the offer, but he eventually bul**** me into agreeing for a R99 contract, and he promised me that my nr will not change. After few days I recieved 2 simcards by courier, went to Cell C store, and on the system were 2 new contracts. One for R99 pm which I agreed to, and another contract for R247.64 pm which I never requested nor agreed to. It wasn't even offered to me. My bank acc was debited with R247.64. I reversed that amount at my bank, and also cancelled the new R99 contract, as I was told one may cancell within 7 days if not satisfied. They cancelled the R99 contract, but not the R247.64 one. They rather added R70 for cancelled debit order. The amount increased to R317.64. They phoned me several times to pay, I explained everything, I made an affidavit at police station, send copy of ID, copy of bank statement, as requested, yet they handed me over. Now the debt collectors phone me 4 times a day, the amount increased even further to R396. I emailed ***** dept of Cell C, but they ignored my query. What else can I do. Please help.