Utah  |  Legal Malpractice

we purchased a home security system back in June. we signed a contract stating that we had only 3 days to cancel our 36 month contract, however, we have not been recieving monitoring because the system doesn't seem to ever work correctly, we also can't really afford to have it, so we want to cancel it. When they sold it to us, we were told that legally we have 90 days to cancel, but calling them today they said we can cancel only if we pay the 36 months in full and pay for all of the equiptment they gave us for "free". do you know what my legal rights are here?