In addition to acting as a standard cell phone, Apple's iPhone has the ability to connect to and utilize a Bluetooth hands-free headset. This will allow you to make and receive calls without using your hands. In order to hear the phone ring with Bluetooth and an iPhone, all you have to do is make sure your headset is properly connected.
Turn on the Bluetooth capabilities of your iPhone. To do this, tap on the "Settings" icon and then the "General" menu listing. Tap on the "Bluetooth" menu listing and press the "ON" button if it isn't already. This will cause your iPhone to immediately begin to search for Bluetooth compatible devices in the area.
Put your Bluetooth headset in "Discovery" mode. To do this, press and hold the button on the side of your headset for a few seconds until the indicator light begins to blink.
Select the name of your headset from the listing of devices that appears on your iPhone's screen. Your iPhone and your headset will now be properly connected to each other.
Press the "Volume UP" button on the side of your iPhone. This will cause a volume meter to appear on screen. Make sure the volume is up to a level of your liking. Now, whenever you receive calls on your iPhone you will still be able to hear the phone ring even though you've got a Bluetooth headset connected.