My iPhone 13 is frozen n it won’t even turn off what do I do

Try to do a Force Restart. It usually takes a couple of attempts to get the key sequence right. On the last step, make sure you hold the button long enough for the Apple Logo to appear. It could take up to 30 seconds.

Force restart iPhone - Apple Support

leave it for the complete charge to finish and start charging it once it starts all set to the normal usage. If it doesn’t start then it’s a hardware issue for the service centre.