Bad partners

I had a 3 year contract with them. It had expired now and they kept on debating on my bank account. I've called them and say i want to down grade, they said i must pay a fee for that which i did not think its worth it. Then i said i want to cancel it and re member i had no contract as i has expired. They said i must pay a cancelation fee which i did but still they are continuously debiting which i do reverse as ive paid what they asked for. Now they keep on sending emails that i must pay and threatening law suit. Is like they forcing me to be in business with them when i do not want