APN settings in IOS 6? (iphone 4)?

I'm having trouble sending/receiving pictures on my iphone. There's a red exclamation mark when I try to send my pictures and I don't ever receive pics sent to me. I reset the Network Settings but nothing happened. I don't know how to adjust the apn and other settings in order to get the mms to work. The phone is not unlocked though. It's an at&t phone and I'm using an at&t sim. Also, where can I get the APN information for at&t?

AT&T's website perhaps?

  • Will it erase my apn settings if i update to ios 7 on net10? As most net10 users know you have to re-enter the APN settings to get mms and Internet on the iPhone. (As well as others. IPhone just makes it more difficult. Lol.) If I were to update to iOS 7 would that mess with them? Or would it stay the same and still continue to work? I want to update but I use mms and Internet a great deal.
  • What should my APN settings be? I have an unlocked AT&T iPhone 4 on the Straight Talk plan. I've changed my APN settings, and everything works except sending pictures to non iPhone users. I can send texts to them, but not pictures. Does anyone know how to solve this problem? Let me know, thank you!
  • What settings will it change if I press reset all settings on my iPhone? Also, will this help speed up my iPhone because that's what I've heard. Because my iPhone has been so slow lately and taking like 3-5 minutes to send 1 text. If you know of any other ways that could help speed that up please also let me know that.
  • What are the APN settings for a straight talk (t-mobile) Iphone? I have an Iphone 4 with straight talk and my data just stopped working for some reason today, i'm unable to use the internet unless connected to Wi-Fi and i'm unable to send or receive MMS messages. Yesterday it was perfectly fine. I don't know what to do! Help? I'm trying to reset my APN settings but don't know the right ones. I've been using wap.tracfone