A vs. An

I was writing something else when I mentioned my cellphone. The questions is, should it be a HTC One or an HTC One?

Actually I've had this question for quite some time, only this time I took action and investigated it finally.

Here is what I find - http://www.englishpage.com/articles/a-vs-an.htm.

USE 5 & 6 clearly explains that it's the sound not the spelling that counts.

So an HTC One it is.