I assume you mean that the rear wheel is tilted at the wrong angle. i20s use twist beam rear suspension so there's only a small number of things that could be wrong.
There's 5 possible causes that I can think of:
- The wheel is bent.
- Rear wheel bearing has failed. This will make a horrible noise when you're driving.
- Twist beam bushing has disintegrated. This is probably the cheapest one to fix.
- Rear wheel bearing unit (or stub axle, as it's also called) bolts are loose and it's coming off. If it's just a larger version of the suspension on the Getz, it will be held on by 4 bolts.
- Twist beam is bent. Usually caused by some sort of accident.
You can test if 2, 3 or 4 are the cause by jacking up the car and pulling on some bits of it so see if they're loose. With the car jacked up, the wheel should turn freely (unless the handbrake/parking brake is on) but should not wobble at all. You should be able to pull and push hard on the wheel and twist it at any angle and it will feel like you're pulling the whole car. If you can feel a knock as you pull the wheel it probably means that the wheel bearing has failed, even if the wheel doesn't seem to move much.
With the car jacked up (don't crawl under it) have a look at the joint/hinge in front of the rear wheel, where it connects to the car body. The gaps around the joint should be the same on both sides of the car. Try pulling on the twist beam near the joint, you should not be able to move it at all. If you can move it, the twist beam rubber bushing has failed.