SIM Slot

I bought my iphone from best buy, paid it off, and made all necessary and un-necessary payments to at&t to unlock my sim card slot. Contacted their supports multiple times and got transffered and hung up on/disconnected. I sent in an email to unlock my iphone and got no response on the first so i ended up making 3 request to unlock, and they said my iphone wont be unlocked becauaw the amount of request and that id have to wait 30, when i had already waited 6 running back and fourth between phone companies and Best Buy. i waited the 30 days and its been at least 4 since i made the new request, which im feelin really unhopeful about. Is there any way at all you guys can help? i was just trying to switch to a cheaper plan and ugh I just payed so much money for it and its like its not even mine. I thank you guys for anything, for reading this; hopefully yall can help.