The dealer can order new lock "tumbler" which matches the set of keys you have...However, the price will be high, $300+..
The other solution is to take the "tumbler" yourself, and find a car locksmith who will open the lock tumbler and fix it to work again with your keys, this could cost $50-$100 depending on what is wrong...
To take the tumbler out, you need to insert the key...there should be a screw on the side of the door that holds the tumbler, take it off, then if the key moves to the right or left it will be released with the tumbler, if not, you need to try moving the door lock nob up and down untill the tumbler released...
If you cannot take it out yourself, the locksmith should be able to do that,
Hope this is helpful