To encourage customers to use a signature based authorization vs PIN authorization for debit card transactions, marketing is considering using a drawing. Customers that switch from PIN to signature will have their name put into a drawing. Winner will receive a monetary prize.
Under GA law, is this prohibited?

Most likely - see paragraph 4:

http://law.justia.com/codes/georgia/2010/title-16/chapter-12/article-2/part-1/16-12-20