If I make a call from the PSTN (through a VG200 gateway connecting to CM with MGCP) to a phone A which has the CFNA set to another phone say B. If B is busy and A doesn't answer the PSTN user gets a fast busy or dead air when the call is hitting phone B. The gateway is sending a correct user busy code to the PSTN. It seems to only be a problem with CFNA. CFB plays the correct user busy signal. The ISDN cause codes seem to be identical in both scenarios. PSTN connection is to BT in the UK.