Wow, we must be really lucky. Our teachers often call in the evenings, even on Saturdays, just to touch base and let me know how my boys are doing. Our teachers very often give their home # and address too. I wouldn't call them at home but have sent holiday and thank you cards.

I'm not sure that they've done it every year but many, many years they have.
My little ds's 1st grade teacher would call me on a Sat to discuss ds (not just negatives, some positives too), we'd end up chatting about Disney, Disney cruises, what to do to keep up his reading & math skills while on the cruise such as miles sailed, show him distance traveling on a world map, etc. While on the phone, I can hear her kids inquire who she's talking to and she'd tell them "________'s mom". Her kids would say, "Oohhh! Let me talk to _________!" (her kids went to after school care with __________ so they do know him.) Once our conversation was done our kids would chat a while.
I can't imagine having to have a face to face meeting for
everything b/c a teacher isn't sure he/she is really speaking to me.
Both have ADHD, one very mild, other severe and has an IEP. Many times, esp for the annual IEP review, we have our conference by phone when I can't get off work. (I work in a hospital so limited # of staff can be off at same time. Dh is not good at dealing with this stuff as he
should have had an IEP himself but instead was beaten daily by nuns; that's another story.) My boss knows ahead of time that I will be 'off the floor' once I get the phone call. The meeting time is planned ahead and though they try to stick to a schedule, it's not always exact. Our CST has day after day of IEP annual meetings and they have it down pat. Some members are there in the meeting room all day, others come and go such as reg teachers, sped teachers, speech, OT etc. depending on the needs of each child. Once they're all assembled, they call my work and put me on speaker phone.
OP: Maybe by email, you and your son's teacher could set a
very specific date and time to have a phone call. Just b/c others have stood you up, don't assume this teacher will also. This way you don't cancel work plans unless you both agree to have this phone call at the specified time. You should also have a firm plan as to who is going to initiate the call and you're both in agreement that the other person will be ready to receive the call.
Good luck!