T-Mobile rebate rip off

I received my notification in the mail today about my $50 mail in rebate from my T-Mobile phone. I was expecting a $50 check, but instead I just got a letter saying they couldn't process my request because I didn't include the original UPC from the phone box. Of course that's crap and I'm 100% sure I submitted everything correctly.

Google "T-mobile rebate ripoff" and you'll find plenty of others with the same experience. They know I have no way of proving anything, so they've got the upper hand and they're using it. I called their rebate "customer service" number, and the operator said that unless I have a copy of the UPC, he couldn't do a thing. I should have known better, but of course I didn't make a copy of that. I have the original box with a big hole in it, but that's it.

I submitted a complaint on ripoffreport.com, but I'm not sure it will do any good. What else can I do?