Well it's not fixed... my idle is back up to 900 and its hesitating again and my check engine light is on

Does anyone know if there is anything i can do as far as making GM do something? I've tried calling them, and they gave me a case number and told me they would call me back and never did (imagine that) When i called them back, they "lost" my case number... I contacted a lawyer and i can't get it considered a lemon because it's not under warranty anymore (i didn't buy the extended) and the problems didn't happen when it was under factory warranty. I don't know what else to do, The dealership has guarenteed me 2 times now that it is fixed... obviously it's not. GM made a big deal the first time i called that i only took it to a GM dealership 1 time and acted like it was my fault that it wasn't fixed.. obviously something is wrong, and the GM woodwrench mechanics can't even figure it out! Is there anything i can do, or am i just screwed?