Acknowledged Negligent Practices will cost the customer, not them

So disappointed in Robert Bunyan Electrical. After giving us an incomplete Certificate of Compliance, we later find out that when he opened the main switch box, he didn't cover my printer (which is use for work) so there's pieces of cement trapped in my printer and now I have to fork out R750 and drive to midrand to get it fixed.

I was also told that he knows that he didn't move or cover the printer but what happens after is not his fault. Feeling so done in right now.