Billed Incorrectly

I was utilising Rain for more than 3 years now and for the 1st time after upgrading to their R101, they billed me before i could get the device, yet they said we pay after usage. 2ndly, after receiving the R101 device, I cancelled online the other device. They didn't bill me for the other device only to double bill me after cancellation. They failed to cancel the 1st device. I am so flabbergasted with their billing and unknowledgeable service consultants. I am glad I cancelled their services.