Multiple lines for same product in an Order Line Item (OLI)

customer is facing the issue in both new order and modify order.  But I am able to replicate ony using modify order. Could you please help me to understand is this an expected behavior, is there a workaround for this to achieve customer’s requirement?

 

Issue description:

Product: ADSL Service
------> (Relationship Name) ADSL High Bandwidth Dynamic IP: Max 1, Min 0, Def 0
                   ------> SmallBIZ Lite - Dynamic
                   ------> SmallBIZ Junior - Dynamic
------> Email Addres: Max 20, Min 0, Def 0

Product Constraint:
[1] Selection of SmallBIZ Lite - Dynamic requires the quantity of Email Address = 1
[2] Selection of SmallBIZ Junior - Dynamic requires the quantity of Email Address = 6