Forced to use a service I no longer want, need or use.

I have been using Rain ISP for a few years and it was actually always good. Until I could not afford them anymore. I was billed for months the Router was completely off since I moved to a rural area where it does not work at all. I NEVER agreed or signed for a contract. I specifically took Rain since it was a month to month. I was told THEY CHANGED IT. With who's consent I would love to know. Now that I want to Cancel it I am told I must pay the arrears of R2500. I do not mind paying it off. But I was advised This must be settled otherwise I should pay it off next to being billed. Does that make sense. When will this be settled. I do not want or need your services. Please cancel my service so I can start paying off the outstanding balance.