Brake caliper question

I bought a car at the end of August that had a few advisorys on the MOT, one of which was 'front near side brake slightly binding'. The garage assured me that all the jobs that needed doing would be, but now 4 months down the line, my brake caliper has apparently seized. Should this have happened? Are they fibbing and just bodged the job? It's in being mended now but want to be armed with a few facts before I go in and potentially make a wally out of myself :o

TIA Michelle