Search online number and address of CBP office in your area

Any CBP office should be able to fix this problem. Remenber to tell them that you have shown the officer on the Port of Entry your I-797 approval but he still dated your I-94 based on the expiration date of your visa, which is an error.

I happened to just go through this process, so if you have any question do not hesitate to ask me. The only thing I request is to tell people how you fix this problem afterwards so other people can learn from your experience, just like you learn from mine.