Sold to Party information in Service order cleared automatically

Hi,

I need a clarification.In my case Service Order getting generated from Sales Order.

Before saving the sales order,in the generated Service order(under schedule lines), Iam seeing the Sold-to-Party is populated automatically.

After saving the order,when I open the Service order, Sold-To -Party field is blank.

Why system is clearing the Sold-To-Party infor in Service order upon saving of sales order.pl suggest me.

Regards

SB