MTN phone contract unjust rejection

I app**** for an iPhone 13 128gig on the online platform for R599 per month. MTN rejected my application without basis only to tell me that they can offer me a contract of R500 only which meant I couldn't be offered my requested item. No further explanation were offered and I know I can afford the R599 contract. It's not just to reject a deal like that without consideration. I would like to get this sorted out and get my desired phone.