http://www.cbp.gov
1/. select " Travel",
2/. select " I-94 "
3/. select " Deferred Inspection"
under "Deferred Inspection ", you will find the service CBP does to correct the wrong I-94 card. In addition, there is a file " Deferred Inspection Sites", you may find a city close to you so that you can go to this CBP site to correct your I-94 card.
I did this before. It is very easy. Before you go, call the local CBP office first to understand what is there is process.
Good luck.