When I call to hire a technician, I lay down the law right there. That way the instance of my telling said Technician what I want after he/she arrives won’t be necessary. The customer is always right. Think about that for a minute.Not unique to any trade.
Imagine a plumber coming to a house to install a new toilet, or an electrician to fit a new light fixture and the home owner telling them how to put it together.
Lots of blokes will be off side and defensive from right there onward.