cell c repair centre

i have a contract with cell c for an iphone 7plus which i recently sent into the repair center and yesterday 27/08/2019 i got an sms saying the assessment on my phone has been completed and a quote has been generated , i then called in to the repair and i was told they currently have no iphone 7 pluses in store and therefore my phone would be replaced with a iphone xs max for 21000 of which exceeds my c surance limit of 12***0 and i will be liable for the R6000 excess fee and i refuse to pay so much for something that is out of my control . cell c has been very *********** about this whole claim thing and ive just been getting passed around from pillar to post and im honestly sick and tired .