Nightmare cancellation process with RAIN.

I cancelled my contract with Rain on the app and the automatic response is that someone is going to call you back to collect the modem. A week lapsed, and no one called, despite numerous efforts requesting a call back. I later dropped the modem at one of the shops and they acknowledged cancellation. I was told that the payment requested was the last debit given that I was on a prepaid contract. Now another debit has gone off, and requesting my money back on the payment was based on prepaid. What prepaid, the past month I had cancelled and I was not using rain. On their system on my account, the next debit is scheduled for next month.