Here is some info from AT&T web site: FAQ
What is needed to use AT&T Navigator?
An AT&T Navigator approved mobile device, AT&T network coverage, and either a monthly subscription to the service or a day pass. We also recommend a data rate plan for route information as standard data charges apply.
What devices is AT&T Navigator available on?
AT&T Tilt, AT&T Quickfire (CTX75), BlackBerry 8110, BlackBerry 8800, BlackBerry 8820, BlackBerry 8310, BlackBerry BOLD, HTC Fuze, LG CF360, LG CT810 (Incite), LG Xenon, Motorola Q9 Global, Motorola Z9, Motorola V9x, Nokia 6650, Pantech C610, Pantech C630, Pantech Matrix (C740), Pantech Matrix Pro, Samsung BlackJack II (i617), Samsung Rugby (A837), Samsung a637, Samsung a657, Samsung Epix (i907), Samsung Propel (A767), Samsung Propel Pro (i627), Samsung A777, Samsung Eternity (a867), Samsung Impression (a877), Sony Ericsson w760a
How much does AT&T Navigator cost?
$9.99/month for unlimited access (including a free 30 day free trial) or $2.99 for a day pass. Data charges apply for route information (average route uses 35kb or about 30 routes = 1MB)
Note: Day Pass is not sold at point of sale and is a self provisioned option for customers who have already used a free trial or canceled a monthly subscription.
Where can I use AT&T Navigator?
AT&T Navigator works in the U.S. including Alaska and Hawaii, Puerto Rico, as well as Canada. Note that international data charges apply for usage in Canada.
How do I find AT&T Navigator on my device?
AT&T Navigator is preloaded on some integrated GPS devices such as the Motorola z9. Go to the Main Menu and click the GPS icon to launch AT&T Navigator and sign up for the free 30 day trial. On GPS capable Blackberry and Windows Mobile devices, click Get Navigator or Get TeleNav and you will be prompted to download the application.
How can the best possible GPS signal be attained?
In order to receive GPS signals, the device should have an unobstructed view of the sky. The GPS signals are not affected by weather and will go through clouds, plastic and glass (with the exception of metal-coated, wire-mesh, and bulletproof glass). But GPS signals do not work indoors; buildings, terrain, heavy foliage, and materials such as metal, concrete, and stone will block GPS signals. In an automobile, it is best to place your receiver on or near the dashboard so that it can receive GPS signals through the glass windshield. Acquire the initial GPS signal while stationary. Be patient, it may take 2-3 minutes to acquire the first GPS signal of the day. Keep the device turned on to optimize subsequent uses of GPS.
How do I enter an address for driving directions?
There are three ways you can enter addresses:
When you select "Drive To" for driving directions, you can either select Type It to type the address using the keypad of your phone, or
"Speak It" to use our Voice Address Entry system.
You can also enter addresses online using your computer by going to
http://www.att.com/navigator and clicking the Enter Address Now link.
If I decide to call in my address instead of typing it, will I use my Anytime Minutes?
Yes, any outbound voice calls made while using AT&T Navigator (i.e. calling in an address) will count against a customer's allowance of voice minutes. However, the BlackBerry devices use integrated speech recognition (no outbound call is made) so speaking an address or search does not use voice minutes.
What happens if I miss a turn?
AT&T Navigator will detect where you are while you are driving along the route. If you miss a turn or make a turn where you shouldn't, AT&T Navigator will automatically re-route you.
How can I increase the volume for the spoken directions?
Use the volume keys on your device to increase the volume of the spoken directions
How can I hear the spoken directions again?
Press the green Talk key on your device to hear the spoken directions again.
How can I extend my device battery life?
AT&T Navigator can use a lot of battery power. Make sure you completely exit from AT&T Navigator when you're finished using it. Always select the End option to ensure you've properly ended the application and it has stopped running.
How can AT&T Navigator help me to avoid traffic?
As you drive on your route, AT&T Navigator periodically checks your route for traffic alerts. If there is a slowdown or other traffic alert, it will notify you and give you the option to avoid that portion of the route.
Can I make AT&T Navigator avoid a specific highway without relying on the Traffic portion?
To manually re-route yourself, press Options and select Traffic Summary. Select the road you want to avoid, and press AVOID. You will then be rerouted to avoid that particular road or highway.
How do I use the Map features?
When you select Maps and Traffic, you can select "Current Location" to get a map of where you are, or you can get maps of previous or new places by selecting "Recent Stops," "Favorites", or "Address."
Can my map get traffic as well?
Absolutely. When you are in the Map view, press Options and select "Show Traffic."
A map is nice, but how do I know the address of where I am?
When you are viewing a map, press Options, then select "Cursor Address." This will show the approximate address of your location.
How do I use the Search feature?
The Search allows you to find nearby businesses. You can search by category or by name.
What can I do once I've found a business with the Search feature?
Once you have found a business, you can get driving directions to that business, maps of the area, read reviews and ratings about it, or call the business itself. You can even save the business to your Favorites.
How do I view reviews on those Businesses?
The Search feature also has a rating system. When you search for a type of business, there is a category for "Most Popular," which will show ratings and reviews.
How do I rate Businesses in the Search?
To give a rating or write a review, go to Tools/Extras and select the business from your Recent Stops or Favorites List. Once there, select the option to "View Reviews." From there you can add your own rating.
How do I find nearby gas stations?
The Search function has two different categories to assist you. The "Gas Stations" category will help you find the closest gas station nearby.
How do I find the cheapest gas?
Searching for "Gas By Price" will allow you to find the best deal within a 15 mile radius.
How do I check for traffic?
When you are looking at a map of a location, press Options, and select "Show Traffic."
How do I share addresses with my friends?
When you select an address in your Favorites list, you will see an option to "Share Address." This will send the address to your friend's AT&T Navigator.
How do I view addresses others have shared with me?
Your Favorites list will have a default category of "Received Addresses" where you can view, move, or delete addresses that were sent to you by others.
How many addresses can I have on my phone?
You are not limited in the number of addresses on your phone. However, you can delete unwanted ones, or move them over to your Favorites instead, through the Recent Places menu.
How do I customize AT&T Navigator on my phone?
From the Tools/Extras menu, select Preferences. Here you can change your routing style, your map display, turn traffic alerts on and off, and make other changes to tailor the service to your needs.