Help!!! Delta Ripping me Off

[kwamboka]

I have a credit with Delta that expires soon and want to use it to reserve a ticket but they are making me buy a more expensive ticket when I can find a cheaper one on their website. They say I cannot use my credit online as I have to speak to an agent and when I do, the agent says she can only find a more expensive ticket and that's the price I pay for talking to her. The cheaper price is still available on the site. I'm already paying a $250 administrative fee for changing flights and now they want me to pay a more expensive ticket!!! Help!! Know where to go from here? I know what they are doing sounds wrong/illegal.