We were away for one week and I saw this number on the missed calls at least once, sometimes twice a day while we were gone but there were no messages on the answering machine.
I have had the same experience as all above.
Let them pay for the call when the answering machine picks up - maybe they will quit calling when their phone bill runs up.
A reverse search, however, says it is a cell phone so maybe they have an unlimited call service most likely. If so, their employees are only wasting the company's time and money.