Rain network.. wrongful debit order

Rain network after 3yrs of our relationship they decided to **** me after I gave them more business.i cancelled my 4g simcard early October after taking on the rain one 5g I was told I will still be billed end of October for the last tym .my network was cut off I even lost the simcard as it was not in use anymore.come 25 November I am being billed again when I enquired I was told that the simcard was being used.by whom as the simcard fell at the back of my wall mounted cupboard during month of September and I have proof that I did send out cancellation query which I was told that it was processed so how come the simcard was being used as it was supposed to be cancelled at that time .I want my refund