AT&T announced a new promotion today that will give you $100 off your bill if you add a new line to your account.

The deal will take $100 off for every new phone, tablet, or mobile hotspot you add to your account. AT&T's promotion is only good from January 29 through March 31 of this year. You can redeem the offer online or in an AT&T retail store.

The AT&T promotion is another example of a growing theme in the wireless industry. There's a battle to keep and grow subscribers, which is why you've seen other carriers like T-Mobile offer to pay cancelation fees if you switch from another provider. AT&T also pays up to $200 if you switch over from T-Mobile.