Change my grade or not? Help!?

How would I go about asking my English teacher to change my previous grade in her class?

I recently found an old progress report that stated I had an A for the first quarter of English class; which was last semester. However, since then we have finalized the instructional time and completed a final exam which decided that my final grade was a B. My grades are still up on the internet, and I recently noticed that my first quarter grade was marked as a B instead of an A. I would really prefer if my grade was an A, as it would give me straight A's for the year. I've noticed several of my peers who got the exact grades for the class as me ( all B's ) and received a final grade as an A! How would I go about informing my teacher about this, and persuading her to change it in the most polite, effective way possible?Change my grade or not? Help!?
Tell her exactly what you're telling me. That you found an old progress report that said you had an A (although are you sure it was your report card, because progress report for me just means halfway through the quarter- make sure this isn't an error on your part) and you were wondering if she could just double check it to make sure. If you are the one with the error, just politely thank her for her time and willingness to check it.