They keep charging me even I send them the cancellation letter as their required.

This is my first experience with such an awful company here in USA. I registered at ballys  3 months ago for a membership where I had access to all Ballys($39.99 monthly). I thought why I just downgrade so I can pay less ($34) I am not using any other Bally. I asked the sales employees there that I want to downgrade ok they told me we are going to make you deal you can pay now $64 and your new membership will be 29 monthly I agreed. Guess what I got charged twice so now I am paying 40+30. I asked the employees why is this happening  they said to me don't worry will solve it. They never did I asked them aging and what the status them pretended not knowing my problem at all. So i deiced to cancel my membership this time I read the contract carefully  they need at minimum 10 Business day prior to next due date.
I send them a certified mail to cancel my membership which arrived on June 4 my next due date was 21 June guess what I was still got charged. I tried times to call them, it is impossible to contact to a human..