I use Scumbumbo's Unlisted Phone Numbers mod to reduce this issue. But even still, the calls are crazy.
It works for the most part, but it won't help against those Sims who do end up with your number. One Sim of mine has so far only given it out to both of her parents, and her mother constantly tries to get a hold of her. She gets phone call after phone call; if she refuses to meet at one place, she'll get another call an hour later being invited to another place. It happens a lot during the middle of the night, too.
I'm not sure what it is about her mother, but her father barely reaches out in comparison. Same relationship level and everything. It gets frustrating.