We had a simple agreement with them not to debit my account on dates not stipulated on my contract, I've had a the same thing done by them in December

We had a simple agreement with them not to debit my account on dates not stipulated on my contract, I've had a the same thing done by them in December. Now they've taken money that doesn't belong to me. I've mailed them but it seems like they don't want to refund me and this was supposed to pay my child's educational trip. It's the middle of the month for me I can't pull any strings and this particular trip is of great importance as it adds to my son's year mark.