Give me back my money

On 1 May 2019 I attempted to purchase movie tickets online. The payment was declined. I used a different card to book the exact same seats and found out that I ended up being double charged as the original payment did go through. I contacted Ster Kinekor and was told that I would be refunded within 48 hours. I have sent numerous emails and called the contact centre. All requested information was sent. To date I have not been refunded. No one is responding to me and I have no idea what to do next. Absolutely awful service and broken promises.