I have Sideline on my cell. This was my first call from someone using the Sideline number I gave them. Even though it showed the 408-290-5339 number (apparently that's Sideline's forwarding service) the caller was legit, from someone to whom I'd given my Sideline number. When they left a voicemail, it showed his actual name and cell number. I guess if they don't leave a voicemail, maybe the caller's number doesn't show. Not sure - still new to the service. But I like it! Works great. Now I can keep my own cell number private. Legit call for me (not Unknown).
Mssed a call from this number, they called on my sideline number. Looked it up found all reports of scam on this site. Went back to phone log and number had disappeared from call log and sideline app. Odd