I was on F1 visa from Jan 1st to June 22nd and then was on OPT from June 23rd to September 30th and then my status changed to H1B visa. I did not get the visa stamping yet.

Can you suggest the tax forms that I need to fill. 1040 NR, 1040 NREZ, Form 8843.

Which one would be the best option in my case?

Thanks a ton.

I am single with no dependents

Yes, you will file nonresident tax return. On the H1-B income, the employer must withhold FICA taxes.

Thanks for your prompt reply. I have an other question:
I got my H1B in October but I did not get it stamped yet. My employer did not hold my social security and Medicare taxes nor I received and social security wages.

How do I tackle this situation. Do I have to pay social security and medicare taxes from my own pocket (eventhough I did not receive any benefits). Do I have to fill any extra tax forms.

I greatly appreciate a reply for this question. Thanks a ton in advance.

You have the legal obligation to TELL your employer that you were liable for FICA (Social Security and Medicare) taxes from 1 October 2009 onward. Do that in writing (email is good for that).

Once that is done, it is up to your employer to fix the problem.