Bad customer service

I once had a two years contract with Cellc which expired in December 2021, I cancelled the contract with them later in Dec then they told me that I must still pay for December billing cause I didn't cancel my contact in time which I paid R600. In January again they tried to debt my account again with R317 which they said is for December billing. then today I called them to ask how much do I owe Cellc then the lady told me that I owe R500 I ask from 317 in January how come now my account is 200 extra she said is because of the unpaid debt orders for January & February which I didn't sign any mandate for Cellc to debt my account in those two months. they didn't call or any SMS notify me about the unpaid but they charge me 200 for something that I never agree on. I need to pay and close this account but am not going to pay extra 200 for something that I never agree on.