well, I can understand your pain with a dealer, I have known a few that also were terrible like what your's seems to be, some of them don;t care about the small guy or know there the only one in the area and as such, don;t care knowing folks need them more than they need you! sad but is what it is some times!
My suggestion would be as you already know,
stop using them, go else where,
there are many GREAT dealers out there, and like I said, a GOOD dealer that has GOOD workers, tends to want to help its customers, as they know doing so, gets them returning customers! which them makes them money!
I will add that however, COVID sure has changed how many things get done, and time frames on , what was once simple
I been waiting on parts now for simple things, for months now at some dealers, , and this is on some simple wear and tear parts too,
and its like that all over NOT defending any BAD dealer, just saying, some times, its out of there hands, supply chains and replacement parts are not what they used to be!
so some times, a LONG visit is out of a the hands of a dealer in the current world sadly!
BUt that said, again, try a different dealer, I would have to think someone maybe can recomend a CAT dealership they love here if asked maybe? ?
as for hearing over the phone??
My father (94 yrs old) is deaf in 1 ear and almost deaf in another, I got him an amplified speaker phone,(land line phone here, NOT mobile) its made a huge difference for him in how he can hear people on the phone now, just recommend if you do so also, buy a quality phone
as the first 1-2 I tried were cheaper and sound quality wasn't so great, I forget what model I got hi, but can look next visit if you like?