Sip.conf question

Hello all:

I just had a question… My DID only supports ulaw and my carrier provider is only supporting g729… I have a calling card setup and I need to have the DID come in with ulaw but ougoing calls for the provider be send g729… I cant seem to get this work… unless i have “allow=ulaw” under general,… here is what I have in my sip.conf

[general]
bindport=5060 ; UDP Port to bind to
bindaddr=0.0.0.0 ; (0.0.0.0 binds to all)
dtmfmode=inband
disallow=all
allow=g723
allow=g729
context=a2billing-CC

[Carrier1]
type=peer
host=x.x.x.x
dtmfmode=rfc2833
disallow=all
allow=g723
allow=g729

any suggestions?