Invoice getting split based on Billing dates. Order to Billing

Hi Guys,

I am having a service material. Item category TAD. (Order to Billing). Each line item has different billing date.

When I do billing VF01 or VF04 it splits the invoice based on billing date.

The client has 15 and 30th as billing cycle.

I want to combine all line items which are due for billing on 15 and 30th.

How do I prevent splitting of the invoice.

Thanks in advance.