How to get a refund for unauthorized Robux purchases on iPhone?

How long does a transaction take to stop pending and how long does it take for a refund?

my little brother got on my phone and bought $200 worth of Robux without permission. I’m trying to get a refund but it does not give me the option to do. I have to wait for it to finish pending to get a refund because I need that money as soon as possible

[Edited by Moderator]