How to release Customer Credit exposure

Hi Gurus:

How to release customer exposure for lines backordered before doing ship confirm?

Detailed scenario is as follows:

Sales Team prepares sales order for 10 MT and then released the order. The item is lot controlled and there are 3 lots available in inventory as follows;

Lot 1           4 MT

Lot 2           4.5 MT

Lot 3          3.5 MT

Based on FIFO (by lot #) system automatically allocate Lot 1 and Lot 2 and backordered the 1.5 MT.

Now sales team wish to add new order for customer having another item which have 1.2 MT available but the system put this on credit check HOLD at the time of release. Sales team is asking that amount 1.5 MT should be allowed, so that customer should get the maximum quantity in the shipment.