Problem in Billing

Dear Experts

I am stuck in a billing issue.

We have Quotation followed by order ,del. & billing in our process.My problem is that when the prices are updated in quotation it is carried over to order sucessfully but when the invoice is created there is no pricing in that.I have checked the copy control settings in order , delivery and billing all are working fine.

But why this problem is occurring.

One more thing is that in my Quotation the item catgy is AGN and when it is copied to order it is TAN and remains TAN only untill the end.Also the manual pricings and all are entered in the quotation level.

Kindly advise.Suggestions would be rewarded.