That phone key is a mute button. Unless you dropped the dough for Ford's Mobile-Ease TM product, you don't have bluetooth in your Expy.
What you need is a Parrot Bluetooth handsfree kit. I opted for a CK3000 Evolution for my 07 Expedition. It does not have a screen (for caller ID), but is black and silver and the actual MMI (man-machine interface) is very small and unobtrusive (about 1.5" long and 0.75" tall).
This is my 3rd Parrot kit (my other car has a CK3100 with screen and my wife has a CK3200 LS with color screen). These things are great. Full Factory stereo integration. When done right, this is how it works: You get in the car, start it (with your bluetooth phone in your pocket/purse, etc), the phone automatically connects to the Parrot. You are driving and listening to a CD or the radio. When a call comes, the Radio mutes the music, and you can hear a phone ring from the Car Radio speakers. You push the green connect button to connect the call and the phone audio comes out from the front two speakers of the car. A microphone is installed in the car (I have mine on the steering column), so you just start talking.
You can buy it here along with the cable to hook it up to your stereo.
QCExp-1 (The cable I ended up using)
QCFCSS-2P (The cable that was recommended by the site)
I installed the interface (a FOB-like dongle with a knob and 2 buttons, one red and one green) right above my cointray in the dash and right below the A/C vent (if I had a 4x4, it would be the switch for the 4x4 modes instead of the cointray). Fits perfectly, and matches my interior (charcoal/black/silver).
If you feel like installing it yourself, you don't need the wiring harness, but if you don't like to cut and splice, you'll need a wiring harness that cost about 70% of what the CK3000 costs.
Just a heads up. The 07 / 08 Expies don't have an ignition switched 12V at the radio (maybe if someone has a shop manual, they can tell me where on the dash there is one), so regardless of whether you get a wiring harness or not, you will need to splice into a ignition switched 12V supply from the fusebox (I just looped the wire on a leg on the fuse).
The website has a finder that will identify the more expensive and more advanced QCFCSS-2P wiring harness that works with radios with a mute, or the a NAV radio. I received this and installed it, but had issues of when the Parrot unit went on, the delay in the factory radio for line input made any voice cues from the Parrot cut off (when I push the green connect button, it would say "Pl... mand" instead of "Please say a command". This is not the fault of the Parrot or the harness, but one of those special conditions of the factory radio.
Sounds like your radio is exactly like mine. I ended up using the QCExp-1 harness instead. This harness still mutes the radio (in fact, when the Parrot goes on, the screen on the radio reads "Phone", whether your radio was on or off at the time a call comes in), but instead of using line-input for the audio (able to control the volume from both the Parrot knob and the Radio), the QCExp-1 hi-jacks the front 2 speaker signals via the harness and Parrot relay cable (under normal conditions, the front 2 speaker signals go through, but when a call comes and the radio mutes, the Parrot supplies the audio through the front 2 speaker wires). With the QCExp-1, I can only control the Parrot from the Parrot knob in between the red and green buttons, and not through the radio volume button.
Works fine that way. The actual "brain" of the Parrot is this blue box that is installed inside the dash, so it has enough watts to power up the Expy's speakers.
Wow, I didn't realize that I just wrote a novel. Anyways, if you were so inclined, you could probably install it yourself. I installed the other two Parrots for my other car and my wife's car, but I got lazy for the Expy and decided to get the harness for it in order to prevent splicing into the factory wiring.