A+ Medical Equipment

I was diagnosed with sleep apnea during the summer of 2010. My doctor recommend that I use a c pack machine so I started to lease one at first then I ended up buying it. But anyway I have fought with this company on their billing ever since day one. I signed up for a payment plan which is 10$ a month due on the 22nd of every month. I have not missed a payment I might have been late a few times but other than that ive always sent a check in the mail. Now their threatening me to turn me in to collections for non payment and I have all my cancelled checks back to prove that ive been making payments. First my bill was 654$. Now I got one Friday in the mail in the amount for 707$ and their stating I havent made any paymnents. Well I got my cancelled checks to prove it and I have called and called and no one will not return my call. The number I call they tell me they dont take care of the billing in that office which is moved somewhere else so I leave my name and number and nothing. This isnt the first time they turned me into collections either. I would like to get a refund back plus the waiver dropped where I owe on the machine. My wife and I both work and I go to school part time and have a three year old daughter. I do not need the extra stress in my life by dealing with these people because their billing is so screwed up its terrible.