Let our customer feed their configuration of U1911 back to us. From the configuration, we found things as following.
1. The prefix 00 is used for international call. And the matching officeselectcode is 3.
2. You have configured two officeselectcode 3 and 254.
3. You have two office for AT0, one is office 3, another is 254. And they have separate officeselectcode.
So, when you make an outgoing call, the process should be like this:
1) The called number begin with prefix 00;
2) U1911 find the matching officeselectcode should be 3;
3) And because only office 3 is match with officeselectcode 3;
4) At last, U1911 choose office 3 to go for this international call.
That mean you only use one AT0 line although you have configured two AT0 trunk.