I'm always tempted to call and say "their driving was absolutely fine, no problems at all"
Though to answer your question, yes people do call them, having been a van driver for a couple of years with a number on the back of the van I had a couple of people call the number about me. (both times elderly people that didn't like me doing 50MPH+ past their house when they lived on a stretch of road with the national speed limit)
One problem with having such a number displayed on the van is that it is open to abuse by malicious trouble causers.
They could invent any story they like about the driver and ultimately, it would be their word against the driver's.
Nightmare, that's why lorries (and possibly vans) have tactometers (spelling?) which records their speeds and times etc, not just to check to see if they're speeding but to make sure they aren't driving for too long with sufficient rests.
i did read somewhere that when you phone the number it doesnt go to the owner of the company but to a call centre and the details then sent to the companies involved, the companies "join" a firm that do it, if that makes sense
It's "garnish".
The road-going equivalent of a sandwich in a pub which arrives with a little pile of crisps.
It's supposed to make you go "Awww, what a lovely company!"
I did once at Parley Cross in Dorset. Some pr@t in a hire van overtook me in the 40mph zone making on-coming cars swerve, stop and flash their lights. This idiot then had to stop in front of me at the traffic lights! A few years ago I might have got out the car but I'm older and was with the wife etc. I rang the number on the back while we were sitting there. The woman just said "OK, we'll have a word with him" and that was that. It was obvious they didn't care and probably wouldn't.
I'm sure they are all good friends back at the yard and would probably just have a good laugh.