Pledge or Arm-Twist

A colleague of mine received a letter on an outstanding philanthropic pledge payment from a campaign that had wrapped-up over a year ago.  Apparently the advancement office’s records showed the donor still owed funds even though there had been no communication in over two years. 

How do you remind your donors about pledge payments?  Do you send an annual letter with an updated status?  Do you make a call to discuss the donor’s philanthropic budgeting and planning?  Do you visit face-to-face?  What is your leading practice for communicating about pledge payments?