We've started getting these calls as well, at varying times in the day. Out mortgage was recently sold to Wells Fargo, so it's interesting to learn that apparently it's originating in some way from them.
Called 2 days in a row. 1st time at 10:12am on April 17th, then next day at 2:35pm. No message was left. Got on web and found the area code to be in AZ. annoying!