I've heard of this happening to late model Yaris' in the past. If I were you I'd ask for the manager and demand for it to be looked at free of charge. There's a good chance that the steering column could need replacing, so it's best to sort if out before the warranty runs out.
If they still refuse to take a look at it, then take the car to another mechanic and get their opinion (just don't let them do any work as it may void your warranty). Then go back to the dealership and tell them that you've had it looked at and that they're going to have to do something about it.
Stick to your guns and don't take any crap from them.I've dealt with dealerships in the past and if there's one thing I've learnt it's that they'll always try and screw you for more money somehow. Take someone else with you if you can, power in numbers always works
Have a read of this, it might interest you. Might pay to print it out and take it to them too:
http://www.toyotaownersclub.com/foru...owtopic=109473