Well, looks like the guy could see the DS3, and also the T1 or DS1 ‘s since there is not mention of them.
The three levels will be, getting the T3 up, then the T2, if the multiplexer uses T2 at all, some muxes go from T3 to T1 in one jump.
After that you need to be sure that the carrier could test the T1 link all the way to the gateway. A loop plug that routes the T1 line back to the carrier at the last point before it connects to the gateway will go a long way to find out where the trouble is at.
If the carrier guy could see the T1 all the way to the gateway, but does not see the D channl, he is talking about not getting the proper signaling protocol on the channel 24 of the T1, the channel used for setup and control from the carrier to the gateway.
Either the gateway is not properly set, your gateway is setuop as master and not as a slave, or the ISDN protocol is not the same on the carrier and the gateway.
Any questions, mike3799@yahoo.