Collective billing in VF06

Hello Friends,

My user generally uses VF06 for billing invoices. For Credit/Debit Memos he uses the same Vf06. The problem is the invoices are been billing collectively(collective billing) he does not want that.

1. If we use Vf06 does collective billing will happen.

2. If so how to stop collective biiling.

Please help me as soon as possible.