re: ATT doubles family sharing...

Mobile Share Value Promotional Plans: Limited time offer. Must request to sign up for or change to the promotional Mobile Share Value plan by Oct. 31, 2014. If you have ordered a new device and have not received it, you may not be able to switch to this promotional plan until you receive and activate the device.
Activate on the new promotional Mobile Share Value 30GB to 100GB plans to receive an allotment of shared data that is double the size of the standard Mobile Share Value plan data allotments (15GB will increase to 30GB and so on). Existing customers must switch to promotional plan in order to receive the double allotment. Customers may remain on their promotional Mobile Share Value plan after expiration of offer. Changes: After offer period ends, if change your data amount, you will lose the promotional double shared data and standard Mobile Share Value data allotments and pricing will apply.