Month to month ****!!!

I upgraded to a month to month router that i was told could be cancelled at anytime as it is not a binding contract. I paid for September and October in advance but my connection was cut in the beginning of October. I cancelled the month to month router on the 21st of October but they are still trying to debit money for November (which i did not use) and December. They are even threatening with legal action. When i contact them on facebook they tell me that they have no record of my cancellation. My sister is also facing the exact same problem with them. Their staff memes are very rude when you go to the store. Take their month to month promotions at your own risk