Changes to the account group and the accompanying partner functions can only be made from a lower level to a higher level. For example, a sold-to party cannot be assigned the function of a payer as fields which have already been maintained for this sold-to party would have to be masked. However, you can assign the sold-to party function to a payer.
The account group for the following partner functions can be changed.
Go to Tx- XD07
have to change the account group from Payer to Bill to Party.
Provide a Payer number as 82.
Set a new account group as Bill-To-Party and Continue.
Change the field values if necessary and Save.