"DONOT START WORK BEFORE RECEIVING UR OPT CARD" And I repeat "DONOT START WORK BEFORE RECEIVING UR OPT CARD"

I had the same situation. Letter from College, Your I797 receipt,Your I20 with OPT endorsed , it's not going to help. I was almost starrting the job before the OPT card in hand but i didn't do that and made a good decision.

Wait for some time..