The "Jehovah's witnesses" refuse the truth that Jesus is God (and have a ton of other false doctrines too), so they are not Christians. Their beliefs lead to eternal torment in the lake of fire.
The truth is that Jesus is God and He died to pay for all of our sins in full (nothing else pays for our sins, not works, not good deeds, not religions, not anything), and then Jesus resurrected from the dead. So the only way to heaven and to avoid hell, is by believing in Jesus for eternal life, without adding any of your own works (Romans 4:5). It is too late to be saved, after death.