Yep, same problem. They keep on calling, never leave a message. It seems the calling company is Mimecast in Massachusetts. I would NEVER do business with a company that makes such a nuisance of themselves.
Even better when you answer the call. Got annoyingmusing for 3 solid minutes (almost as though I had called THEM ansd was waiting on hold). When someone finally picked up the call they just disconnected me.
They call often but I never pickup on my work cell. I called them back and spoke to reception and asked them to remove my name and number from their calling list. Hopefully it will do the trick.