What the actual F!

I had a MONTH-TO-MONTH contract with Rain back in 2020. I stopped used this simcard the moment we put fibre in our flat. (Meaning the simcard was no longer being used, so no billing should be attached to it anymore) I received a call from some lawyer firm today on behalf of Rain, claiming that they have handed my account over for non-payment. Are they mad?? What are they handing me over for?? I have not used the simcard for 2 YEARS!!!!!!!!!!!!! I happen to log into my Rain account and saw that I have an outstanding amount of R1411,67. How?? But yet when the lawyers firm called me they mentioned they're handing me over for R700 odd. ***! That's not all. There were no invoices/charges for the whole of 2021 and 2022. All of a sudden Jan and Feb 2023 there are invoices/charges!! What the actual F man! Where on earth does that come from? I am NOT paying ****! I NEED someone from Rain to call me ASAP!