Check with your future employer if they can allow you to start working with your OPT despite the mistake. If they say yes, make a copy of your EAD card and send the original back (fee should be waived due to immigration mistake, also attach a letter asking for expedition). It probably takes as long as your first time. I went through this process since the gender in my card is wrong. My employer didn't care too much about it. Actually the INS officer also told me to consult my employer if they could accept an EAD card with mistake.