An
intelligent network service, handled in
SS7 networks by an
SCP. Either the
A number or
B number of a
telepone call is changed according to whatever the service is set up for. For instance, the
B number 0800-PIZZA-HUT could be translated to the number of your local
pizza emporium. 'Local' would be determined by your
A number.
This is how all the Freephone, national rate and personal numbering services work.