I would need to know more about the AT&T service you are talking about. If these are analog phone lines, just like the ones people usually have at home, you would need to connect those to blue pairs of the respective cables leaving the 110 block for the jacks you want the analog phones plugged into.
I somehow get a feeling there may be a phone system involved here (24 cables), maybe made by AT&T (and therefore very old) where you would need to connect every port of the phone system to the blue pair of every cable that goes to the extension phone set. Be aware that most old AT&T systems actually required two pairs for the phone operation because the phones required power and so you would need to use blue and green or blue and orange pairs, depending on the pinout of the jacks at the phone locations.
I am sorry - this question is impossible to answer without knowing more about what you are trying to achieve. But, for your reference, take a look at the 110 block wiring diagram to see where the blue, orange and green pairs would be if your CAT5 cables terminate on a 110 block
Dmitri Abaimov, RCDD