I was having a problem with my serger; it was making weirdly loose stitches so I called and asked if they repaired sergers and they said they did so I brought it over, only to have the guy repeatedly INSIST that they do oil and cleaning, that I should do their oil and cleaning service while I desperately tried to get him to look at and understand the problem I was having. I asked if it would solve the problem and he said yes, and that it might be a timing issue, but he was dismissive about my concerns and I was unconvinced that he was knowledgeable of this field. I obviously spent hours trying to fix it myself to no avail so I left it with them to "fix". It turns out it that the needle threads were just not securely threaded through the tension disks and that would have fixed everything.
I don't appreciate that they took $80 to reoil a machine that was only a few months old without even looking to see what the problem really was. An experienced person could have taken one look at it and seen that the tension disks were not threaded and told me that honestly. It makes me feel like they don't care as much about making repairs for people as they do about gleaning the fee for a routine cleaning.