Rate Category Splits the Billing Period

Hi,

I would like to calculate the discount with latest value applicable at the end of billing period. I have defined a discount operand with selection at the end of billing period. I have defined the discount key with value 10 for 365 days.

I am trying to bill the customer from 01.01.2011 to 30.06.2011,

There is a change of rate category on 01.05.2011

Discount operand (discount key) maintained at installation facts Discount key =0 then discount key = 10 from 01.05.2011 to 31.12.9999

While billing expectation is system should calculate the discount as per value at the end of billing period 10 for the total billing period 01.01.2011 to 30.06.2011.

But in actual system is splitting the billing period in two parts one is 01.01.2011 to 30.04.2011 and 01.05.2011 to 30.06.2011 and calculating the discount only for the last period 01.05.2011 to 30.06.2011

Any suggestion why it is happening and how this can be rectified as I would like to calculate the discount for the whole billing period (data set-up is right),