Taking back hardware after cancellation

Besides the shoddy levels of communications and service, ADT has proven to be a very poor service provider. After a break in during March 2013, I entered into a contract with ADT for home security. I physically purchased most of the hardware (at great expense). Upon cancellation, ADT took back the hardware I had purchased (apparently there are terms and conditions relating to this). and I received no buy back or refund! This is totally unacceptable.