I signed the lease with the wrong price

Hi, I signed my lease renewal after asking for a rent reduction because it went up too much, and they sent me the lease with $50 even less rent price. So I signed it because I thought they were giving me more reduction and I even gave them the check, but they called me 2 days later and told me the price was wrong and want to send me a new one with $50/month more. Is this common? I obviously don't wanna pay $50/m more and wanna keep the one that I already signed. Can I do that based on the fact that I already signed? If anyone has any idea, please help me out! it'd be much appreciated.