How does Pip's discussion with Jaggers disabuse him of the notion that Miss Havisham has been his patron?
In Chapter 39 Pip has the totally astonishing and traumatic meeting with his real benefactor Abel Magwitch, and in Chapter 40 Pip goes to Mr. Jaggers' office to confront him.
"I merely want, Mr. Jaggers," said I "to assure myself what I have been told, is true. I have no hope of its being untrue, but as least I may verify it."
Jaggers is characteristically cautious in his reply, but he acknowledges that he has been representing Magwitch in Pip's behalf for all these years and that Miss Havisham was not involved in providing any money for Pip's advancement in life. Jaggers pretends to believe that Magwitch is still living in New South Wales. He very obviously does not want to know anything about his client's possible return to England, although it is clear to the reader that he does know about it.
Pip will later go to confront Miss Havisham to express his indignation at the way she has led him to believe that she was his secret patron. She confirms his accusation but does not seem to care in the least about his injured feelings--or the feelings of any man.
Ironically, in making Pip a gentleman, Magwitch has also made it impossible for him to accept his fortune, and without the fortune which was part of his great expectations, Pip feels he cannot marry Estella. Dickens does not explain exactly why Pip, as a gentleman, cannot accept Magwitch's money, but it must have something to do with the fact that the money was earned by a convict transported to Australia and who is risking hanging by coming back to England in violation of his sentence.