Removing a Jailbreak without connection

Hey!

So my iPhone 5S recently stopped charging properly - I've had to really push the cable in hard to get it to charge or sync. I read on the net that it would probably be due to lint stuck in the phone. So I got a small key and wiggled it around a bit. Now it doesn't charge or sync at all >_>'

So I have to send it to Apple, however my phone is jailbroken...

Is there a way to remove the jailbreak without connecting my phone? I tried to update iOS to the latest version but it isn't finding it in the Software Update section (I imagine the jailbreak removes the internet check for latest iOS versions?)

Thanks,
Marky