Do disbelievers automatically go to hell?

As far as I know, If a Person is not a muslim, then He or her has not chance to go to Jannah. If the person is a disbeliever because he has never known the existence of Islam, then he can be accepted into Jannah. My question is: Let's say there is a Christian, and he knows the existence of Islam, and he respect it as a religion, but he still holds onto his. This person spent all his life helping others, doing a lot of volunteering in Africa and in Asia just to save and help lives ecc... and sacrificing his whole life for others. Now, is this person still not accepted into Jannah? does he really have to spend the eternity in hell, even if his life was full of only good deeds?