You normally would setup 2 extensions at your provider.
Route one DID to extension 1 and the other DID to extension 2.
In the OBi register SP1 to exten 1 and SP2 to exten 2.
Route SP1 to PH1 and SP2 to PH2.
This is how you can do this in Callcentric.
I don't know about F9.
Another option is to route the calls based on callerid.
If a geographic area only calls one DID you can route calls by one or more area codes to PH1 and all others to PH2.