Polycomm Video Conference ISDN issue

Hi Guys,

I would appreciate any help if possible or even a pointer in the right direction.

I have a Polycom VSX 5000 with an ISDN adapter.

I can make Video Calls via ISDN to National numbers, but not to International numbers.
When i try, the call fails, with a message "call has ended". I have tried the Polycom test numbers but these have the same result.
I haev contacted Polycom who asked me to check the Location ISDN International Access settings.

They are currently set to the following :

Country: Ireland
Language: British (English)
Internation Dialing Prefix: 00
Country Code: 353
STD Code: 01
Always Dial Code: selected


I need to use ISDN due to network constrants, I would love to use IP, as this works perfectly, but its not possible at the moment

Polycom are being zero help in this so any help would be greatly appreciated.

Cheers