Poor customer service

I have been having some issues with Rain since March 2020. We got it thinking it wil be great to have Rain as a service provider, but since day 1 we already had some trouble connecting to the router. Rain has a billing date every month and we lost some money using them, we have been calling them and mailing them alot but we get no response. We decided to change the card number so that they can't keep on taking money every month. We also send them an email again to say we no longer want your service and if they can please stop the 5g simcard. Now they have put a debt collecter on us and he/she keeps calling us but then he/she ends the call seconds after it started. We can't seem to call them back. Rain has been sliding down the South African ISP rankings and is now rated as one of the worst Internet service providers in the country (according to me, google and alot of other people).