Well, it does indeed sound like you need staff. You're a good mechanic who needs a good receptionist/girl friday. She (yes I'm politically incorrect) could take calls allowing you to work 3 hours in the morning and returning 1 hour of calls, then do that again in the afternoon. She could even relay phone info back and forth if need be while you are underneath the car and you wouldn't have to stop working
Good people are hard to find but it could work.