Individual Invoices have been created for each sales order

The customer has created 12 sales orders and run the autoinvoice program using below parameters for auto invoice master program.

Sales order Low : 25000000

Sales order High : 25000012

Customer : Gateway Hotel

The requirement is to generate a single invoice for the 12 sales order. However 12 invoices have been created for these orders.

When I check the grouping rule it has been used as "DEFAULT". There is a header level DFF in the Sales order and orders have been grouped based on the date specified in the DFF.

I need not to group the orders using the DFF attribute.

Kindly provide a solution

Regards

Di