Cash back breach of contract

Buying the car went great..... Getting my cash back now that's a different story. My contract went live on 4 April. Cash back is due 5 to 7 working days which means payment was due no later than 15 April. Since the 16th I have been in contact with Nissan Milnerton's Principle, Manager and my sales person hoping to get a resolve. The only feedback I am getting is my payment is awaiting release. So either the director's holiday is taking preference over his customer's payouts or cash backs are used to fund Nissan Milnerton's cash flow.... Why else is it so difficult to release a payment that was contractually due by 15 April 2026. Financing houses should also take note of the breach of contract, in my case it's MFC. Surely this should be a serious offence keeping customer's funds instead of paying it out?? Waiting to hear if the admin/finance team of Nissan Milnerton will find the time to get the payment released or if this will drag out to tomorrow or the next day or next week.