Try this if your phone fails to ring during incoming calls.
INSTRUCTIONS & INFO
If you are transferring a phone number from a prior provider to the AT&T Wireless Internet, it may take about four days. During that time, you can make calls immediately on your AT&T Wireless Internet. However, you must keep a phone plugged into your wall jack to receive calls on your old service until your transfer completes. Make sure that your AT&T Wireless Internet is NOT connected to your in-home phone wiring. Note: Check transfer status at att.com/port.
Make sure that your home phone is powered on and connected to the AT&T Wireless Internet. Note: Dial #21# to turn off call forwarding, if it is currently on.