Paid for Electrical Diagnostic, Trunk still not working.

I went to a Certified Chevrolet Dealer in hopes of getting my trunk fixed
properly, instead it resulted with me having the same issue, the next day.
Before they began work on my vehicle, I explained to them that I replaced
the trunk fuse on multiple occasions and that it would work for a little while,
then the fuse would blow and the trunk would not open afterwards and that I
believe it was an electrical issue and that there could possibly be a short
somewhere. I explained this to them hoping that they would do a thorough
check on the wiring and not just check the fuse box and change the fuse. I
paid $200 dollars for the diagnostic. When I went to pick it up, I was told 4
fuses where changed (windows and mirrors also were not functioning
properly at the time) and they could not find anything wrong after doing the
diagnostic. The next day, the trunk fuse was blown out again. So today, I
took my vehicle in once more and was told that I have to pay another $200
to do another diagnostic plus the cost of whatever work needs to be done.

Should I ask for a refund or pay again to get the same diagnostic done?