T-Mobile Rebate Scam - They want me to come up with the screenshot, which they removed already! Internet, Internet

In Dec 27, 2011, I purchased two Samsung Galaxy S2 White phones from www.t-mobile.com. They had special web only promotion for the white S2 for $99.99 after $100 rebate. The price I paid in total plus tax was $432.48 for two phones. ($199.99 x 2 plus tax) I've just received the rebate cards and they are only $50, not $100. So I called T-mobile, and now they are telling me that they've never had the promotion for $100 rebate, and want the "proof" of the promotion. They want the screenshot of the promotion which they removed long time ago. What can I do?