I was at an Apple Store today picking up a Mac that needed fixing. While I was waiting for them to bring it out, I overheard a conversation between an Apple "Genius" and an elderly man who was buying an iPhone for the first time. He said his old phone that he had for 10 years broke, and he wanted to buy an iPhone to do FaceTime with his grandkids. The guy was unsure about most of the features and generally unfamiliar with the iPhone. The genius asked him if he takes any pictures, watches movies, or plays games and he said no. The genius then asked him how many people he plans on calling on it. I wondered why this made a difference so I listened closely while standing nearby to hear the explanation. The old man said about 10 people, and the genius told him that to fit 10 phone numbers he would need to buy the 64 GB. He was hesitant but said ok and the genius walked off smiling. When he came out with the iPhone he whispered to his buddy who laughed, I'm assuming he told him what he did although I couldn't hear. I felt like explaining to the man how he just got swindled while the guy was in the back but I did not want to implicated in the whole thing, but I regret not saying anything now. I am going to question the next Apple purchase I make. This is appalling.
OP I feel for you. It's kind of a tough one. In todays world you have to be very careful about how you butt into people's situations. If I had came into the conversation from the middle, then I would not have said anything, because I don't know what was said before I heard anything that prompted the 64GB recommendation.
Now, if I heard the conversation from the very beginning, then depending on the situation, the most I would do is make a quick statement to the elderly gentlemen, and my next action would be based off the elderly man's response. If he's receptive and wanted to know more, I would gladly explained it more. If he was defensive, annoyed or anyway wondering why I was in his business, I would have moved on. At least then, I know I tried to do something.