User has an overhead project where the rates keep coming from the the default employee rates instead of the $0.00 set in the fee schedule for the project.
This is happening because the fee schedule does not allow zero ($0) rates unless you enable the option Allow zero (0) rates in service fee schedules in Global Settings > Billing. Otherwise, Core uses the rates according to the Rate Hierarchy. Check this option if you want to use the zero rates from the fee schedules. You can use such a fee schedule to have both the bill and cost rates default to zero, but still keep the entry billable, if required.