Trouble with cancelling the internet service from Rain

While I used them, which was several years everything was well. If your payment did not go through your service was cut, which is understandable. When you start you do an immediate payment. There after you pay at the end of the month. Now when you want to cancel it. You cancel it and the app says it is cancelled. No further information is provided. I googled because I heard of people that kept being invoiced, even though they cancelled. I learned "on Google" not by information provided by Rain that you need to return the equipment to them. As soon as I learned this I returned the equipment. They only cancelled when i returned the equipment. Now, a month after cancellation I receive another invoice, while for that month no internet or equipment was used from Rain. Now they say October payment is for usage of September. Which could not be since I started I paid monthly. So their service is good. But when you cancel it is like a friend told me. They expect you to keep paying even if you do not receive any service.