After over 10 years with AT&T, I will be switching carriers because of the egregious lies and poor customer service associated with a recent "free upgrade". I have been receiving mailings for almost two years now, since my last phone upgrade was four years ago in November of 2010, telling me that I was eligible for an upgrade. While my iPhone 4 was working well, I wanted faster processing speed, so I went to my local AT&T store to get the 5s...
I spoke with a sales associate who assured me that I WAS eligible for an upgrade, it WOULDN'T impact my current plan, and there WOULDN'T be any additional associated costs besides the new device. I paid my $100 and took home my new phone...
15 days later at the end of my billing cycle, I saw a $40 "one time upgrade fee" on my account. SURELY, THERE HAD TO BE A MISTAKE. With years of good-standing history with the company, I took it on faith that they would remedy the situation. NOT EVEN CLOSE. 
- Spoke with the store associate: He told me that AT&T's been adding "upgrade fees" since he's been there and there's no way to remove it. Not Comforting.
- Spoke with the manager: After I explained the original transaction, he called me a liar, telling me he "just didn't believe that the conversation would happen with his staff". Not Curtious or Customer Centered.
- Spoke with AT&T Customer Care: They told me to speak with the store. Refused to transfer me to a supervisor because "it would do no good anyway". Not Helpful.
I have been blatantly lied to about the terms of my upgrade. This is the last time I will be duped by AT&T.