Cannot cancel

After having sureswipe for a while but battling with connectivity and other issues we decided to cancel our debit card machine with them ( it took me three days to get hold of someone to do this ). I cancelled on the 9th October so we needed a months notice . Payment was taken of on the 15th October for that month and then payment was taken on the 15 Nov. Now they telling us we owe them for December to . They are disgusting and I will be taking this further.