Use locked iphone 4 with straight talk?

I recently bought an at&t iphone, and a straight talk micro sim. When I try to use the sim card, it tells me I'm blocked from the network. I know for a fact it is not stolen, because a very good friend of mine sold it to me right after he left at&t and switched to sprint. I was told I would not need to get the iphone unlocked if it was an at&t iphone, but now they tell me I have to.So, I requested an unlock on the at&t website, and when I realized it would take 5 to 7 days I just decided to go into the store. They couldn't unlock it there but they told me I could use a gophone service with the iphone until it did get unlocked. My unlock request was denied, so I called customer service and they told me I could not get it unlocked because I was using the gophone service. They could do absolutely nothing to help me, even though it's their fault I'm in this dilemma. I was told that jailbreaking it may work, but I really don't want to have to resort to that. Is there any reason why mine has to be unlocked when it seems like no one else who has used an iphone on straight talk has had this problem?

Its simple, first get a galaxy s3 and thats it: D

There are plenty of people who are dumb enough to use Straight Talk that have had that problem. There's plenty of sites that are filled with people whining about Straight Talk problems. You get what you pay for.