fix the locked seatbelt

This isn't a change one thing and you're done issue :-(. You will need to replace all of the pretensioners (even the unaffected ones - these are part of the safety system, so the cars tend to blow them all even without someone present) - even if your vehicle doesn't deploy the airbags, and there are no people in that seat a lot of cars trigger them all as a precaution. The other major part you need is a new black box; sometimes you can send them out to be reset, but some can't be readily reset and you absolutely have to replace them.

You also need to check for additional SRS codes, such as airbags, before installing a new ACM/black box or reinstalling the reset one. If anything is off, it will store hard codes and potentially cause issues with the reset or replacement part. This is not an option - it's a MUST.

If you do take this on yourself, you need to let the car sit with the battery disconnected for 15-30 minutes, given you are messing with the safety systems, as one slip can blow something like an airbag up and at best, make for a costly error - at worst, injure you!!!

Once you replace the pretensioners and airbag control module (sometimes called a black box), the only way to clear the error is with a scan tool, which can clear SRS/Airbag codes - this will cost you a cool $300+. This is the one I use: https://www.amazon.com/XTOOL-Automotive-.... If you opt for another brand, ensure it can reset airbag codes.

I'll see what I can do in terms of finding the service manual for your car, but Kias are notoriously hard to find, as they often put them behind a paywall, and manuals for newer models are not easily leaked, unlike those for older models. That being said, without the year, I'm stuck as the 2015 QL uses a different manual than the 2011-14.