Had an idea. Most everypony's had a job where the customers were...unpleasant, in some way. And everypony's been a customer- and probably an unpleasant one at some time, even surely without meaning to be. So, what's your job and how can the rest of us be less terrible to you? Try to keep this advice general (Not just pertaining to youu) so it can be readily applied; and not obvious- e.g. "Don't let your kids kick the employees"/"Don't swear like a sailor at the employees" etc.
Preamble: Presently working in a call center. Despite daily, hourly, complaints from coworkers about callers, have found that if we call receivers speak very pleasantly, so do the callers. In nine months, have never once been cussed out, and this in an occupation where it happens fairly frequently to others. So that's on my people (Mostly? There's surely other call receiving jobs in which the customers are just reliably awful. As there's pretty much everything.)
Actual start: When calling questions/support, what you lovely callers can do so is... I've one request...just one... please...don't hang up on us, it's heart breaking. so mean!! If others don't get sad about it like I do, it still ticks them off and that'll effect how they speak to the next caller. If you call someone for help, how can you just disconnect without warning? and often when the call receiver is mid-sentence...
Even if someone's trying to upsell you hard (And that sucks.), just say goodbye, okay, maybe that person will be less annoying to the next caller.
And when the receiver isn't trying to sell you anything...trying to tell you things to save you money and always beginning with "Do you have time..." or "Have you heard..." or "Would you like to hear about..."... jerks jerks unforgivable jerks who just leave so mean my heart no
tl;dr
Don't hang up on call receivers, it makes us sad, say you're finished with the call and goodbye and THEN leave! your turn.