Yeah, it's a big, often cited complaint about how sales-men are helping to slow the grow of Windows Phone due to talking customers out of it. It's a big issue, and often is a result of training (the sales people are typically told to push so-and-so product relentlessly). I remember when the Lumia 900 went on sale, I tried picking it up just after launch day. Sold out. But then the sales rep started to try and talk me into an iPhone 4S. I said, "No, the Lumia is $100 cheaper." THEN he tried selling me on an iPhone 4, citing the internet connectivity issues on the Lumia 900 as a reason...
I then got smart with him and started talking about how the iPhone 4 had a hardware connectivity issue and had 8GB less storage than the Lumia, meanwhile, the Lumia was getting a software update in a few days to address the issue, AND all customers would receive $100 credit for incontinence (effectively making the phone free on contract).
I was thoroughly irritated, but that's because the iPhone was AT&T's love child at the time, all the sales reps were trained to get everyone sold on it. In more recent years, at my local AT&T Store anyway, they seem to be more neutral. They're always biased towards whatever AT&T's current flagship phone is (I.E: whatever phone gets the big store displays and front window ads), but mostly are more neutral to phones in general. Could it be improved? Most definitely. While they now won't try talking me out of a Windows Phone should I mention it, before the conversation is started, they're always pushing some Samsung phone or the iPhone.
Meanwhile, other carriers aren't educating their employees about Windows Phone at all, meaning the sales reps are completely in the dark about it and therefore are going to try and pitch what they already know (slamming Windows Phone in the process). I'm hoping it improves, but for now, it pains me to think of all the people turned away from Windows Phone due to uneducated, untrained sales people...