How to turn my previous ATT iphone4 to Straight talk?

I have an iphone 4 and it was with ATT but is no longer activated because I can't afford it. I would like to be able to turn my iphone to work with Straight talk, so does that mean I have to pay to get my iphone unlocked? If so where do I find out about the process/prices/ who do I even contact?
Once it is unlocked how do I get it to straight talk service?

Go to the company. I'm sure that they will turn it.

  • Still possible to use att iPhone 3GS on straight talk? I have an AT&T iPhone 3GS with no SIM card. I have looked online and it seems straight talk is no longer offering AT&T SIM cards, only tmobile ( i really don't want to use tmobile towers!) My question is basically how do I get a SIM card for my phone that will allow me to use AT&T towers? Please be as specific as possible a link / how-to won't hurt my feelings!
  • Replacing iphone4 screen att vs verizon? So i'm going to purchance a screen replacement kit for my iphone screen since it is cracked. I have at&t. Does it matter that I get an at&t specific glass screen or do the verizon/sprint ones fit the same?
  • Locked ATT 4s on straight talk? I seen online that I could use a locked att iphone 4s on straight talk as long as i buy the mico sim card that straight talk no longer sells. I bought it on amazon and i activated it with straight talk but when i put in in my phone it says no service? What do i have to do?
  • Is the straight talk iphone4 worth to buy? I don't have enough money to buy iphone 5 from straight talk so is it worth it to buy from straight talk iphone4 and how much will it cost for iphone 4 minutes permonth so do they do credit check on straight talk iphones?