I just missed a phone call from this number. I did call back but it doesn't ring. It justs beeps and immediately ends the call. My guess is that they are spammers, a legit business would answer and not ignore.
I get daily unknown calls (never caller ID) from spammers or VOIP calls when I trace them. Even though my personal cellphone is on the DNC registry, it seems I'm an open target for idiots, despite the fact that my cellphone is used exclusively for my surgical practice!
"Are you receiving threatening calls from the IRS?" Hung up immediately. This is my business phone and caller ID said "RSQUARED" We have a vendor with a very similar name, so I had to answer.