Essentials For Home review: Can not cancel membership

I ordered a Stealth sound amplifier and was offered a $15.00 rebate but after clicking eyers, and finishing my oder I discovered that the rebate offer placed me on a trial membership to some Essentials for Home for 30 days. I immediately tried to call and cancel the membership but the line has been busy ever time and I have tried for several times to call. What can I do? The will start charging me in 30 days unless I cancel.