Wow, you are utterly clueless. You really should not have a car, since you clearly know nothing about handling such matters.
It works like this: If you owe MORE money on the current car loan than the wholesale trade in value of the car is, you can't, unless you pony up money from YOUR pocket to cover that difference. So, if your car is worth as a trade in, say, $10,000, but you still owe $12,000, YOU would have to PAY $2,000 just to be rid of your current car.
The fact that you don't say, likely because you don't KNOW, the current trade in value of your car, and what your current loan balance, further suggests that you are clueless about such matters, and should just stick to riding the bus, where someone qualified will make the decisions for you.