I've experience a terrible situation with old mutual where on the 26/07/23 I've made a payment of R800 with a wrong ref no of which the money is lying by the old mutual account but they refuse to revert the money back to my account cause I've paid through

I've experience a terrible situation with old mutual where on the 26/07/23 I've made a payment of R800 with a wrong ref no of which the money is lying by the old mutual account but they refuse to revert the money back to my account cause I've paid through std bank app. I've been trying to send proof of payment but up to today my money is still lying with old mutual