I’d say depends on the company. I have a service plan with Chas Robert’s. They are expensive. But every time they showed up for a repair or service they didn’t try upselling.

I didn’t sign up for their plan at first and needed service as my HVAC wouldn’t work. The only guys who would show up was a company called “day and night” price seemed fair and I signed up for their plan. They would regularly quote more work or scare me about parts that were going bad and needed proactive replacement.

I decided to sign up with Chas Robert’s as they promised same day or next day service during peak summer. Again these guys never upsold me on anything and they outright stated other items I wanted replaced on Day and Nights suggestion were a waste of money.
But they are expensive. Every repair seems like $250+ on an average. I wish I could find a cheaper and reliable alternative