Shoddy workmanship

Blind Designs had a motor replaced on a roller shutter door. When RS Doors removed the old motor, it was found to be a Centurion motor. We asked RS Doors to replace it with the same motor. They accepted this, and we waited for more than a month for the motor. It broke down, and repaired, twice, now a third time we have been waiting since the 28th March for the motor. I have sent messages, no reply, phone calls aren't answered. I managed to speak to Quinton, the owner, who was very rude, who insinuated that this was now our problem as we wanted a Centurion motor. The job was accepted by them for this motor, and paid in full. If they didn't want to get us this motor, why did they accept the job, they could have said no they don't use that motor They accepted the job and must now honor their commitment