Owing 3 months cause they didn't cancel the service if the payment was not received

I'm really not happy with rain debit system. If they don't debit they need to cancel the service or give me an option to ask for some time. Now I'm sitting with 3 months bill without knowing. I can't sit and check my statement every month to check if rain has debit or not and the excuse I get it I used their service. If it's month to month, why don't they cancel the service if the payment didn't go through? Isn't that how month to month suppose to work?