Isn't Straight Talk just a no contract prepaid telephone? We've been using AT&T Go phone. We bought the phone for $10 on sale at Walgreens about five years ago. I just looked at Walmart and they are now $19.99 but they do have sales. I buy 1000 minutes for $100 and it's good for 12 months. That's it, no taxes, no extra costs, unless you can talk more. We usually have a lot of time each year left and they started having roll-over with your minutes.
The first time when I bought the phone I called AT&T to set up the account. They gave me a phone number, I put $100 on my credit card and they mailed me a sim to put inside the phone. Haven't had any reason to call them since. Once a year I go online to my account page and buy another 1,000 minutes for $100. They have regular smart phones but the minutes are more expensive and I have a home computer for that. If you want just a simple flip phone, this is a great plan. Here's the phone I got for $10.
Prepaid Phones, Tablets, & Plans with AT&T GoPhone