Refuse to pay a shortfall to my refund

I've been struggling to get my full refund from Houss since December 2023. I've been renting for my son the students accommodation at The Campus Auckland Park for the past 4 years. In 2023, I've put in a deposit for my son who signed up for a 10-month lease effective 1 Feb - 30 Nov 2023. Houss short-paid me by R3,310.20 from my deposit. I've been trying to make the attempts to get the balance of my refund since 2 Feb 2024. Instead, someone by the name of Jumari from their Finance keeps sending emails which have no relevance to my query. I emailed their refunds department the lease agreement, proof of payment and the signed outgoing room inspection form, but no one at Houss has the willingness to address my refund issue. I've also picked up they billed my son some R450 they claimed was for plumbing. There was no plumbing that took place in his unit and I was also present when the outgoing room inspection was conducted. I have been made aware that they charged this R450 for all students who rented at The Campus during 2023. Who charges money without providing a service? What a ****!