Spoke with Gary about setting up an appt.

Spoke with Gary about setting up an appt.
He informs me that earlier in the day would be best.
I inform him that doesn't fit in my schedule as afternoons are best.
His response is well the latest he is comfortable setting up an appt is 1pm because they may be backed up from a.m. work and may not be able to get to it 1, and depending on the a.m. work that day, possibly not get to it at all that afternoon.
So I can't help asking what the purpose of setting up an appointment is if there's a possibility that they are unable to keep the scheduled appointment.
He reiterated the a.m. work concern.
I informed him I'm a third shift person and wouldn't be able to make an a.m. appointment and added that if I make an appointment (as with anywhere else) I would be expecting the service at the time of the appointment.
I thought this was reasonable, but it seemed to slightly agitate him.
He calmy, with slight frustration said "ok, I can't guarentee that it will be seen at the time of the appointment, but we'll do our best.
I politely reiterated my expectation that if I make an appointment I will be expected it to be worked at the schedualed time.
(Personal thought: People do have other responsibilities in life, ya know? Thus the purpose of setting scheduled appointments)
So, after stating my expectation, he was clearly agitated (by what I feel like is reasonable expectation) and it became clear that he no longer wanted to discuss etiquette, and asked in a flat, irritated tone "would you like to make the appointment at 1?"
He said this with a demeanor in his tone as if he almost preffered I'd say no because I'm not a convenient customer, but also knows better to express that. But in his tone and approach, that demeanor was clear to me as I had in the past obtained a psychology degree, and generally can read ppl well.
I feel like my interest in keeping an appointment is legitimate, and if there is no guarantee to keep the scheduled time, it should not cost me my valuable time, or possible trip back to the dealership.
I called Greene Chevrolet, and I asked if there would be any concern (due to a.m. work) that my appointment would be possibly pushed back. The gentleman said (with absolute confirmation) "No, if you set up an appt at a specific time, that is when we will begin to work on it.
I explained why I asked, and he said, based on diagnosing the problem possibly taking a few hours, and his crew getting of at 4:30, that he would want to make the appointment no later than 1pm.
I shared with him, Gary thoughts were 1 at latest also, but not for possibly taking a few hours to diagnose, but rather in the case they are backed up.
He offered comfort to say, "no, you bring it in at 1, and we will start on it at 1."
No questions of are you gonna hang around, or drop it off, after discussing a time for appointment.
No juggling work.
Just straight forward businness.
So, I called back Gary, said I need to cancel my appointment. He said "ok." I said thank you. Gary said "ok" and hung up.
Glad I called Greene Chevrolet to see if they aren't juggling clients work, and are commited to keeping an appointment.