What does 2 Corinthians 12:17 mean?

Paul is responding to an accusation made against him and his associates by some in Corinth. This would have been spurred on by the false apostles among the church. The accusation seems to be this: Paul refuses to accept personal donations as a tactic to make the Corinthians feel guilty, inspiring them to give Paul even more. Another possible implication is that he is planning to steal some or all their contribution to the suffering Christians in Jerusalem (2 Corinthians 8:10–21). Liars interested in tearing Paul down would have suggested his refusal to "burden" the Corinthians was a crafty way of deceitfully getting the better of them in the end (2 Corinthians 12:16).

Of course, Paul was not doing this. His conduct, and that of his fellow ministers, showed no such sin. Most likely, the false apostles made the accusation as cover for their willingness to take money, even though Paul would not do so.

Now Paul asks them flat out: Did I take advantage of you through anyone I sent to you? He has in mind Titus and another man mentioned in the following verse. He seems to be asking if they have any evidence, at all, that they were cheated by Paul or any of his messengers. In short, they do not.