Nimble and Cell C are crools

Guys Cell C and Nimble group are really ****** regarding my account with Cell C that I owe R210. 00 while I paid off my contract with them now they say I must speak to Nimble group of whom I don't know, and to my knowledge cell C has never communicated with me to cover their lies they said they communicated with me during September 2023 and I paid off the account during 28th of December 2023, guys I need serious help regarding they want me to pay Nimble group and definitely it won't be the amount they say it is cause they will add on their admin fees, iyooo please people help in this situation