You probably can't ask for one particular service technician, but if you could you would want Ivan.
I had a condensing unit (the outside portion of my air conditioner) that was abnormally noisy. The manufacturer provided NO help or even guidance. Ivan heard the noise and tried many things. On the 4th visit (I think - I lost track of how many) he solved the problem by isolating the fan shroud from the top of the cabinet with self-sticking foam tape. I will not fault him for the number of visits, as he had to follow normal troubleshooting procedures. I DO want to applaud his persistence. If the rest of the techs are even nearly as good as Ivan, I highly recommend Gardner Plumbing & Heating.