Functioanl area wrongly deriving in the MiGO Document

Hi,

I am facing issue in the MIGO FI  Document  showing wrong  Functional area. .The Purchase order is Cost centrer PO and it including two addtional condtion tyes for fright cost and addtional condtion types GL accounts  Cost center is deriving from OKB9.Now the issue is when i was creating the MIGO document that time the addtional GL Account aganist Functional area is coping from the purchase cost center functioanl area not from the aginsist cost center functiional area

EX:

Puchase order K  1000 Functional area 1000

addtional condtion type gl acccounts Cost center 2000 and functional area 2000

based on this when i was doing the MIGO that entry is showing like this

GL          Costcenter     Functional area

gr/ir  a/c            

labour exp   1000              1000

Fright a/c    2000             1000

adtionalcost      2000             1000

Here Cost center againist 2000 having functional area 2000 but the system deriving 1000

note: cost of sales a/c not activated

Any body can help on this