I work for that carrier in the UK. I wrote the VoIP switch that you are working to – right down to the H.323 stack, so I understand it very well.
I have looked at the traces of your calls, and I can confirm that our switch is not extracting the dialled number from your call.
If it helps, the logic of the switch goes like this:
In the H.225 SETUP message, the switch looks for the presence of a DestinationAddress element. If one exists, then it takes the first addresses, strips alphas and uses that as the destination number. This will also happen if the first entry in the list is an H.323 ID.
If DestinationAddress is not present, then the destination number is taken from the Called Party Number element of the Q.931 SETUP message.
I have been trying to recreate your problem with an AS gateway, but I cannot manage it.
We have many customers using Tenor gateways and none of them have this problem.
Unfortunately, the product you are buying from us does not include any remote configuration service. But, I hope this information is helpful.