I keep getting letters from a company called Pension Benefit Information with that phone number listed to call and confirm personal information.  Each time I try to call to find out  more information (before agreeing to provide any information!) I get a busy signal.  I just looked up the number on the Better Business Bureau (I actually googled the phone number and saw it listed on the BBB website) and it seems legit, they list a toll free number to call - (800) 283-7373.