IPhone 5 SIM Card Error (iOS 7.0.0)?

Hi, I recently updated my iPhone from an iOS 7 Beta to the actual firmware which was released. I struggled with the updating, getting error after error on iTunes until it finally let me update. Now on the setup screen for iOS 7, I get as far as sim card verification where I encounter this error:

"SIM Not Valid; The SIM car that you currently have installed in this iPhone is from a carrier that is not supported under the activation policy that is currently assigned by the activation server. This is not a hardware issue with the iPhone. Please insert another SIM card from a supported carrier or request that this iPhone be unlocked by your carrier. Please contact Apple for more information."

Now, this sounds like a routine "unlock your phone" answer. But the problem is, the SIM card was working perfect up until I updated to iOS 7. Right now I just want to be able to use my phone, even if it means downgrading to iOS 6.x.x. Is there anyway I can possibly bypass this? Can it be unlocked from its current state or do I have to downgrade? Any suggestions?

Model: A1429

Kik: OmgItz_JP for additional information!

Added (1). Okay, so what I really wanted to know in the case that the phone definitely needs to be unlocked, can it be unlock from its current state? What will I have to take to get through this?

There's no way to downgrade to iOS 6. X, make sure your iphone is unlocked if so you can ask the carrier get a new sim card or ask them for help

Ask your carrier for help, but if you didn't reach to a solution may be you need to unlock your iPhone. Try the website that my friend has used it to unlock his iPhone for permanent.
it seems they are official apple unlockers.their price was about $25 and they did a remote unlock by

getting the iPhone imei number. They unlocked my friend's iPhone in just 12 hours.

take a look at their website: http://officialappleunlocker.com/