I paid for some lessons in advance but now it looks like I won't be able to do them all. So I want to tell the teacher to give me my money back (in a polite way).
My ideas are something like either お金を返して下さい or お金を戻して下さい but I don't know if it's correct and polite.
How do I say
Please give me my money back
in a polite way?