I have a iPhone 4 ios 7 but I have no personal hotspot?

I have a refurbished iPhone 4.
Updated to ios 7 (Newest update.)
Its a AT&T phone running on Straight Talk prepaid (sim card)
Please help me figure this out? My boyfriend has Verizon iPhone 4 but he has a personal hotspot… Why don't I?
Help would be amazing!

People say to go to
Settings > General > Network> activate from there
but I don't have a network setting after General? Maybe I'm just STUPID. High possibility. But, My Network is prepaid so its TFW network (I saw this from going to my ABOUT in generals)…

Any help would be greatly appreciated.

It could be an AT&T thing. If it is prepaid they may not offer that for those customers.