I got the same Bluetooth for my wife and I (I have the Evo 4G while she has a different phone) and the Voice Calling options work great on her phone (with either of our Bluetooth devices) but do not work at all on my Evo 4G. I have a nice Jawbone Icon and I hold the button in and get the "Voice Dialing"prompt on my headset but nothing happens on the phone. If I go to the Voice Dialer app on the Evo 4G then everything works fine but I have to manually open the app on the phone.
On my wife's phone (and on my previous phone, the Instinct) I am able to just hold the headset button in until I get the prompt and then say the command and the phone reacts.
The problem is not with your phone. This feature is not yet working on the Android 2.1 Operating System.
The good news is within the next few months, maybe sooner, the Android 2.2 Operating System has this new feature. The 2.2 O.S. is code named "Froyo" and it is already running on a few of the HTC EVO phones that are in the hands of the developers and some tech savy users.
To get it working before the "official" release, you must "root" your phone and then "flash" it with the new 2.2 O.S.
I for one am somewhat tech savy, but I think I will wait for the official release.
Here is an article that reflects what I am telling you.....
Hope this helps. I am anxiously waiting for this feature as well.....
I think there are at least 2 work-arounds.
1. BlueAnt Q1 or V1 Bluetooth Earphones.
2. BlueAnt S4 SpeakerPhone.
I haven't tried them on this phone yet, but I have heard that they work with phones that have VoiceDialing. I used the Q1 with my Palm Pre with some success, (the voice dialing was limited because my Pre didn't have built in Voice Dialing, but I still could use the 6 or so built in assignable voice dialing shortcuts,)
I am thinking about going to BestBuy and trying the BlueAnt S4 Speakerphone, but have not made up my mind yet.
BTW, there is also a Vlingo SafeReader app for the Android phones, that will speak any text messages to you and allow you to speak any text messages to send out. It is a $9.99 app, and I haven't tried it yet either.
I have a Jabra (latest version) and it doesn't work with the EVO either. The EVO voice dial works very intermittently stand alone although it works great with my Ford Micorsoft Sync. The voice recognition software on the EVO is weak.