There are two sides to every story, and we are only hearing your side.
I used to be an engineer and have seen some down right dangerous stuff in the past, I put my hand in a cupboard once looking for a light switch that the customer told me was just to the right, only to put my hand on a live mains JB with no lid on it. This was on a takeover and the JB was feeding the spur for the panel. I have also seen cameras lashed in because a staff member is suspected of stealing.
I take on board that it is not good especially if you work for the company, but you have to ask yourself why would they use service guys to install if the job was not a rush job? I have installation engineers and service engineers and the only times I use one to do the others job is exceptional circumstances.
I suspect that your company has lots of problems though, because my team would come to me if they found that, not plaster it on a forum and knock approved companies.