A good solution to this is cellphone apps such as "TrueCaller" (not-affiliated to them, just a good app.). People that have opted-in automatically have their th

A good solution to this is cellphone apps such as "TrueCaller" (not-affiliated to them, just a good app.). People that have opted-in automatically have their their phonebooks uploaded to the central server. So, for example, if your business were to call me and I mark it as "Business ABC" then all other users of the app that get a call from you would immediately know it's from "Business ABC" despite you never having called them. It's worked so nicely since I got it, I'm surprised we ever did without it. I think it also auto-disconnects calls from numbers that a sufficient-amount of people have flagged as spam. The only problem it doesn't solve is when a business decides to do it's surveys/telemarketing through the same number it attempts to contact clients on. This is especially rife with SMS spam, where they use the same number to SMS you valid "updates" that they use to send promotions/ads and other spam.