Beware and don't send any personal documents or sensitive information (like passport, PAN, credit card, bank account, etc. Yes it is ok to withdraw your acceptance.Honesty is always the best policy in this case. It can also make it easier for you to draft up an official acceptance letter in response. This letter serves as an offer of employment to you for the University Support Personnel System position. Did you apply for a job there in the first place? If not, its a fraud. I am writing to confirm my acceptance of your employment offer on April 20 and to tell you how delighted I am to be joining XYZ Corporation in Chicago.