Possible wrong format being sent to the Telco.
Take a look at the posting below. Same trouble report.
Hope this helps,
Please rate helpful posts.
MAYBE IT IS TOO LATE TO REPLY but it can help for other admins on the future.
I had the problem with calls to cellphone, some cellphone, the problem was wiht the way to dial, some cellphone has to dial direct like your house. That was my problem, it was not problem for my router or pbx.
I attach my debug from the router it sends the legend "Cause Value= 42"
Hope it can helps u!