Straight talk sim doesn't work

I have an iPhone 3GS factory unlocked with every firmware backed up. I bought a straight talk sim for iPhone 3G-4S on Walmart.com. When i registered my straight talk sim with an activation card it didn't didn't work aka NOT RECOGNIZED on their website. I put the sim in my iPhone and nothing came up i tried airplane mode 10 seconds didn't work. I tried a lot of things. Please give me some information that i could possibly use W/ my phone so i don't have to buy another.

Your iphone isn't unlocked, it might be jailbroke but not unlocked.
the straight talk sim card if for tmobile, so you need a tmobile phone or a unlocked att phone.

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