I switched all 3 over our lines from TMobile to Mint Mobile this weekend and went from $175 per month to $45 per month - a $130 per month savings. And since we were already on TMobile and Mint Mobile uses TMobile towers we aren't noticing any difference - I've had mine for 4 days so far and it's been great.
Unlimited talk and text and yes, only 4gb of monthly data but just keep your wifi on your phone on and it will use wifi at home and so basically no data. I've had mine on the plan for 4 days and used zero data. Leap of faith, yes... but so cheap and getting very popular. PLUS we are saving $130 per month!) You switch and you get $15 credit (a month free basically) and so do I. Ask me any questions you might have and I'll try to answer them. My referral link is here... http://fbuy.me/rn_hw (you have to use it to get the $15 month free and for me to get it too.)