AT&T has a $100 Credit with select SmartPhones when signing up for a new qualifying line activation. Switch carriers and save a bundle. Free Activation too.

New AT&T Family Value Plan - 4 lines, Unlimited tax & text, 10 GB of shared data $160/month. 2 lines for $130. Expires Soon

Smartphones that qualify include:
Samsung Galaxy S5 $199.99 + Free $100 Credit

Samsung Galaxy S4 Free + Free $100 Credit
Samsung Galaxy Note 3 refurbished Free + Free $100 Credit

Samsung Galaxy Mega 6.3" Free + Free $100 Credit

LG G Flex Curved smartphone $299.99 + free $100 Credit

Moto X $49.99 + free $100 Credit

iPhone 5s $199 + Free $100 Credit
iPhone 5c$99 + Free $100 Credit

Be sure to read: How to Find the Best Smartphone Plan in 2014

Terms:
New and existing customers are eligible when you activate a qualifying wireless line

Add a new line for any smartphone, feature phone, tablet, wireless home phone, mobile hotspot, or other connected device

You must remain active and in good standing for 45 days; your credit will be applied within 3 bill cycles