Everyone you spoke with is correct. I don't see that the agent was rude for advising you that the record would be documented as he may have inferred that you would call again and try to get a different agent to book without the fee. I just changed a ticket yesterday, same orgin/destination but different connecting city and I paid the expected $100 change fee.

I'm sorry but I think you should consider the possibility that the disagreement was escalated the discussion by telling the agent they were wrong and then attempting to "correct" him. When he didn't agree with you, the agent becomes rude?

There is always more to the story on both sides.