Terrible service!

Monday I received a phone call from Vodacom to notify me that my upgrade was due. During this phone call they asked me what phone I would be interested in upgrading to? I specified that i would like the iPhone 6s+. They told me this wasn't a problem and they will be happy to help me that day and they have put my phone aside. I got to the store later that day, after being told I need to up my contact in order to keep a 24month contract instead of a 36month contract. I further needed to pay off my old handset as this was an early upgrade which Vodacom did not explain to me when they called earlier that day! After all the paper work and the push to make me pay more money, they proceed to tell me they don't have the iPhone 6s+ in store! I don't understand why you would phone someone tell them to come collect the phone, tell the client it has been put aside for them, for them to get there go through all this trouble to be told they don't have that phone! Further more no one takes responsibility, it's everyone else's fault. Such a disgrace!