Matthew 18:23
The dude was forgiven, but refused to forgive his fellow man. So he lost all his forgiveness. I mean, think about it, ALL that he had been forgiven came back on him as a debt that had to be paid.
And then in that psg, it says that he was "turned over to his torturers UNTIL he paid the last of the debt"
Some people say that could be talking of Hell, not Purgatory--- or not just Purgatory--- since we cannot pay the whole debt of our sins... Only Jesus can (and then only if we LET Him). But some theologians say it is about Purgatory since the dude can get out after paying the debt. (There's no getting out of Hell)
I wouldn't take chances, if I were you... that the debt can even be paid at all. And again, it certainly won't be if one is not in Christ.