12/23/16  11:56 PST  Don't you love it?  ID is "Invalid number" and has an invalid prefix too.  No message left.   Hopefully, anyone with caller ID will not answer any of this type of caller.  It is unfortunate that some older folks don't have or use caller ID and/or answering machines....My 96 yr. old mother happens to be one of them.  Wish we could do something for them, but all we can do is verbally warn them and hope they listen to us.