Klaus, thank you for pointing me in the right direction with SIP trunks, got it working so thanks! Basically I did exactly what you said:

- Dialled number

- Match that number to a registered user (had to create a new table for that)

- Lookup user

- Replace dialled s@ with original number dialled

Works like a charm, however, I have a question over speed and performance. As this is a SQL query and not held in memory is this SQL lookup doing to cause me problems? It's not a big query at the moment, but it could get quite big as I will need to map each number to a registered trunk.

Many thanks,

Keith