I need a new att phone?

I am on a family plan with my mom, dad, and brother. My brother has a iphone 4 with unlimited internet and txt messaging. I had got an iphone and tried to get the same plan but att has the grandfather clause saying two people on the same plan cant have two smartphones. I want another phone but it cant be a smartphone since i can have unlimited internet and i like to use things like twitter and facebook that uses up a lot of megabytes. Anyone know any good phones I can get or what I should do?