charging port MacBook air

The back charging port on my MacBook Air 13" stopped charging the Mac a while back and reading about it I assumed the charger had somehow been 'configured' to the front port due to regular use. However, on taking my Mac into the apple shop for other reasons, I was told that this issue was my fault due to 'charging the Mac in a warm or moist room'. This is an absolute joke as I don't live in a particularly 'moist or warm' house, and there was no 'don't charge your laptop when it's warm outside' disclaimer when I bought the Mac. I CANNOT accept that this issue is my problem and think it's disgusting that Apple would blame an obvious design flaw like this on my use of the laptop. Has anyone else experienced this?