Misleading

I am so disappointed, Rain is misleading and dishonest. When I took a router and I was told that I will pay R625 every month, they said its month to month and not a contract. I pay for usage. To my surprise I haven’t used it for 3 months and they told me I have to pay R1800, today I checked and I am owing R2500. What happened to paying for usage. What is month to month?. How do I owe? I have not used their service so what am I paying for? Why isn’t it explained upon taking the router that you pay even if you don’t use it. This is very wrong. I want to cancel their service, this is totally unacceptable.