Lock problem is my fault.

I had burglar proofing installed last year on my windows and a security gate on the wooden door. The installers initially knocked out a hole in the metal door frame which looked bad. They then installed a lock cover secured by pop rivets. The lock was working fine. After a week the lock started to catch on the cover and this resulted in my breaking a key off in the lock when I tried to open it. The installers replaced the lock and used a hammer and chisel to make the cover bigger instead of filing it which looks terrible. They took the keys for the new lock with them saying that it is an excuse for me not to pay the outstanding balance. The branch that supp**** the burglar proofing is Rustenburg and the salesman is Hagen. The installer also said that I have done something to the lock cover to cause the problem. I'm still waiting feedback from the MD as promised.