找誰去要（Amounts paid by or in behalf of borrower)

我買房時的合同中有這麽一條：
Amounts paid by or in behalf of borrower:
Adjustments for items unpaid by seller
County Taxes 01/01/08 to 6/16/2008 $4000

我現在收到稅單$7000， 按理我應該隻付$3000

我應該是找SELLER 還是我的MORTGAGE COMPANY去要這筆$4000