This is a known issue with DeltaWMS, and the workaround is to delete the old rates that have a ChargeTo date set. Please do this by doing the following:
Select the 3PL tab at the top of Delta
Open Charge Group Maintenance
Open the Change Group for that account
Find the Rate you wish to delete in either the Rental, RDH / Receipt or Picking tabs
Select to highlight this Rate
Press the minus button (-) on the right of the screen
Say Yes to delete
If you are unable to delete the charge by following the above instructions, please raise a new case online and reference the title of this article.