(Telecompaper) AT&T has introduced a new unlimited wireless data offer. From 12 January, new and existing AT&T consumer wireless customers with a smartphone who have or add AT&T DirecTV or AT&T U-Verse TV will be able to sign up to the new AT&T Unlimited Plan, getting unlimited data, talk and text for USD 100 per month. Additional smartphones cost USD 40 per month each, and a fourth smartphone can be added at no additional cost. Tablets connected to the plan will cost an additional USD 40, or USD for 1GB, while watches will cost an additional USD 10.