Quoting
jk
the OP being late on payments or even missing them does not give a co-signer any rights to repo the car. It would only allow them rights to sue for the money.
Green Tempo, this can get ugly if you want but there are ways to do it. Don;t know where your parents live but if outside the city limits, there are often more than one police force that has jurisdiction over an area and do respond to calls. If there is, I would sugggest talking to the other police force that can cover the area.
What your parents are doing is illegal (at least with the info you have provided). I would give the police one more shot at it and ask them to assist you in you picking up your car before going further.
You can file with the DMV for a new title and have it sent to your current address so that is not a problem.
If the police refuse to help, even with proof it is only your vehicle, I would contact the prosecutors office and speak to them about filing charges against your parents for one of several possibilities;
theft and/or conversion come to mind but there may be other appropriate charges possible.
Like I said, it can get ugly.
I would strongly suggest you work this out with your parents rather than going this route but it is avaialbe to you.
One other thing that may urge them to release the car.
Speak with an attorney and ask him/her to write a letter citing proper authority for them not maintaining possession of the car and the legal consequences should they continue to not allow you to claim your vehicle.