Poor standard and service

Just a little over a year since the alarm system was installed and after NUMEROUS Technical issue. From poor wiring and sensor installation..... Yesterday I logged a call after testing alarm system and reported a fault on 1 of the panic buttons (can't explian the detail here),but now they telling me I should pay for a call out on ****py installation done, where most of the "new system" was recycled parts of an old alarm system from when I bought the house(years ago).So a full new system was not installed.Because of the poor installation the alarm triggered at odd times...resulting in me paying additional call out fees as well. They had a nerve too tell the service provider that installed the system is no longer used by them,because of complaints/issues whatever.... I will be requesting legal assist as this is unacceptable service and business standard, if they do not come up with an acceptable solution.