Please post what you think would be a letter requesting this refund here, and I or someone else will help you to correct it. Today is July 15, you still have some time.
I am not a teacher.
P.S. If you don't know how to start, here is some help.
Name of the institute
Department to which you have been accepted.
Your file number
Dear Sir/Madam or if you know the name of the person in charge, that person's name
Then tell them that you wish to apply for a refund, give your reasons, the amount of money you have paid, and thank them for being co-operative.
That should be all you need to do.