Repeated calls with no message, caught by online blocker.  Sometimes the calls are anonymous and are automatically blocked. More recently they start with this number and try a few numbers in less than 1 minute, probably mutliple entries in an autodialer trying to get around online blocker. They use weird unblockable numbers (like 1000000000) in calls after the first to get phone to ring - as such "invalid numbers" are not fully blockable. Telecrooks for sure.