In cases 1) and 2) of 5.2.3.1 if all the indicated traffic channels are available, the user shall select them for the call.
In case 2), if the user cannot grant any referred access channel, it shall select any other available access channels associated with the D-channel and on the same access, to replace the unavailable preferred access channel, or select all the channels on another interface controlled by the D-channel.
Note - Whether only the B-channels that cannot be provided should be changed, or if all the channels can then be changed is for further study.
In case 3), the user shall select any available suiTable access channels.
In case 1), if any specified access channel is not available, and in cases 2) and 3) if insufficient access channels are available, the user shall send a RELEASE COMPLETE message with cause No. 44, requested circuit/channel not available or No. 34 no circuit/channel available,respectively, as described in 5.3.