Salvation is freedom from sin. It is a common condition throughout the world. All of man's efforts to eradicate it have failed. The jailer, though free, was imprisoned, enslaved to sin. Yet those who were in prison, were truly free.
Sin is impossible to cast off by one's self.
It is stuck to us. We were saved from the penalty of sin. But it is process which leads to the eradication of the presence of sin when we are transformed into eternity. Paul said that we need to use our freedom in order to serve. Many people cannot serve because they are not saved.