You must be logged in as admin.
On Topaz version 1.4.0.12 and later,
there is a "Recost calls from" button,
under "Setup -> Properties -> Rates ->". Click on the button and you will be prompted for a
date. Costs and prices for all calls from that day onwards will be recalculated.
If you have an older version of Topaz, it is recommended that you upgrade to a
more recent version where the facility is available.