HTC - Speaker comes on toward beginning of calls while phone at my ear

Has anyone had their HTC phone when you pick up a call, suddenly change to speaker setting and then get an absolute horrendous blast of volume in your ear? I've never had this with any of my verizon phones before. Having the phone switch to speaker setting like that while I'm holding it to my ear, has given me immediate vertigo, nausea, (and worse) and hearing loss that hasn't come back. I thought my face maybe pressing on the speaker button, but the manager at the store said that the screen should go black quickly when it senses the phone is at my ear, and at the store when she checked it, it did. This has happened about 7 or so times, and I've had the phone for a couple of months now.

Admittedly, I am not that technically savvy, and my husband pointed out that I can put the phone back to the dial pad screen and take it off the screen with the speaker. I just don't know if it will happen regardless, or it will continue to happen if I forget to do that. Sometimes I like having the option of taking a call back and forth from speaker on or off.

The employees at the Verizon store was fantastic, and I should be receiving a new phone in only 2 days. But I am still curious if anyone else had an issue like this, or if it is just a defective unit. It's a great phone otherwise. I've been happy with all of my Verizon phones so far, as has my husband. My previous phone was a droid razor and I never had this issue, nor with the Verizon phones before that one. I recall the screen going black and my face never seemed to touch the speaker button.

Otherwise, this is a great phone.