Following design should be changed:

Scenario in MS Dynamics Finance -> Accounts Receivables:

• NOTE: parameter "advanced auto charges" at Commerce paramters in "Commerce&Retail" module is active.
• A new sales order is created at a call center - > sales lines get also related charge lines from type "per Pcs"
• Next I go into CPOS and select the sales order for a pre-payment processing
• After processing the pre-payment transaction on CPOS the system automatically changes the type of charges"per Pcs" to type "Fixed"

The amount totals would be still ok for the moment -> but if user changes quantities on affected sales line after the pre-payment was made the charges amount would not be updated cause it´s just stored as a fixed amount now and not as a dynamic amount anymore.