Not honouring warranty of installation

We recently moved to Blue security and they installed a new alarm for us, we kept 2 sensors from the previous alarm. The alarm kept on going off due to kitchen sensor (one of the new ones they installed). We called Blue to sort out the problem within a week of install. The Blue technician came through and adjusted the sensitivity on the new sensor and fixed the problem. Blue security charged for this call out which was due to an installation problem. Despite numerous requests this has not been credited and is still showing on my statement. Now debating on whether moving to Blue Security was a good decision after all.