AT&T spent $1bn of this giving 200,000 staff a $1,000 bonus and improved healthcare, is spending another billion to boost capital expenditures, and the rest looks like it is going to shareholders and the company cash stockpile.
So lower prices for AT&T products/services to customers aren't in the cards and only more money for the stockholders. One would think that if they cut their prices to reflect the tax rate drop they might pick up more customers and thus grow some more business, or spend some of those remaining billions (not just one billion more) to speed the system upgrades. But then again, the stockholders only look at things one quarter at a time.