Easy Curves not honoring their money back guarantee

Purchased the Easy Curves exerciser which came with monthly supplies of vitamins. I have emailed them at the time of the first refill and cancelled the autoshipment. And sent back the vitamins to get the refund. They claim they have not received it and I need to prove that it was returned. Why? They supposed to guarantee money back even if I just had the empty bottle. *** Finally, after 3 months I did get a refund - maybe this posting had to do something with it?