Upgrade incompetency

My father is one of Mtn's first customers. Loyal, business account holder. Today he went for a upgrade at Mtn Shelly Centre. Asking for a iPhone 6s. Him being of the older generation didnt specify that he wanted a 128gb. Just assumed that seeing that he currently owns a 128gb that is what he will receive with the upgrade. Because they didnt have stock, Codey gave him a 16gb!! ***! From best to worst! Why didnt he inform him that they dont have stock and would he be satisfied with a 16gb? He just showed him the phone. All my father saw was iPhone 6s. I really feel that he should have advised him on choices available. But he doesnt owe a iPhone, thats why he doesn't know a 16gb is useless! I am a Vodacom customer. Had my upgrade done in December. I phoned Vodacom and had my phone couriered. I didnt specify i want the 128gb. That guy knew it was the best, thats why he send me the best!!<br> The managaress, Roxanne, also said unfortunately they cannot exchange. IPhone is still sealed in its box! Unfortunately Mtn was off line the whole afternoon, but tomorrow my dad is going to cancel his contract. It will be sad that Mtn is loosing one of its first customers!