Quickbooks doesn't allow both classes assigned to line items and invoices?

I need classes assigned to line items...but this has nothing to do with my question.

Shipping field's <<<<< look at my image above, that is being set automatically,  go to setting advance and in the drop down you choose the revenue account shipping goes to, there is no other way to change its class.

From the QB API side of things the shipping field is considered a lineitem, but I cannot get it to change its class.