Hmmm, 6 years on the road traveling full-time and I have ALL my work done on the RV at the campground by mobile RV repair.
Have NOT run across one single one that was not professional, knew their job and kept in touch with me regarding appointment.
Perhaps you are calling from classifieds listed by handyman and backyard mechanics?? Totally different breed of repair people. Not to say that all are but usually most don't have a business to run they are just out to make an extra buck. Just saying.
BTW: If you are at a CG the best and IMHO the only way to procure a reputable Mobile Repair is to go into the CG office and ask who they use/recommend. They know and use the best one in town.