Membership Cancellation difficulties

I mailed off my cancellation form that I printed off from my online account with LA Fitness back in May 2015. I stopped getting fees drafted out of my account shortly after so I ASSUMED my cancellation form was received. Now, here we are in August 2015 and I just go a bunch of LA Fitness membership hold fees, on top of that it caused my bank account to go into the negative which caused overdraft fees from my bank. I am extremely frustrated and upset. I had to file a complaint claim with my bank again LA Fitness.