On VG224 , you can choose asymetric G711 codec with the voice service voip command for the fax issues.

voice service voip
modem passthrough nse codec g711alaw

The modem passthrough commands will determine the G711 mode used for outbound calls

But the following part of config will determine the codec use for inbound calls :

dial-peer voice 15 voip
description <=== avoid PVID 0 in VG224 ==>
answer-address .
modem passthrough nse codec g711ulaw
session target ipv4:<<loopback_address>>

So in our case , the incoming calls will considered in g711ulaw and outgoing calls will be treated as g711ulaw