Change me to

Change me to
 

situation:

A student could choose either course A or course B. After choosing A, John changes his mind, and now he wants to send an email to tell the staff; can he say this?:

-Please change me from course A to course B, thank you.

CHANGE doesn't sound very good, but I can't think of a better word.

Your request sounds fine.

More formal:
Please alter my selection from course A to course B.

Thank you~