cost control callback

from The Free On-line Dictionary of Computing (8 July 2008)

cost control callback

   <communications> A system where a computer automatically
   rejects incoming {dial-up} calls from certain telephone
   numbers and calls them back, with the result that the caller
   pays nothing for the connection.  This differs from security
   {callback} in that it applies to certain phone numbers instead
   of to certain user names.

   (2003-07-13)