[tsac]

The options although listed on the BB are network functions. It may be possible the Storm OS level does not function the same on the ATT network. You could try a different OS level if one is available you want to try.

You will notice in the following info from RIM, the requirement to "send" this info to the cell network so it may be OS related.
I know this is not much but maybe it will help.

Call forwarding
About call forwarding
Depending on your wireless service provider, one or more call forwarding phone numbers might already be available on your SIM card or
BlackBerry® device. You might not be able to change or delete these phone numbers or add new ones.
For more information, contact your wireless service provider.
Forward calls
To perform this task, your wireless service provider must set up your SIM card or BlackBerry® device for this service.
1. From the Home screen, press the Send key.
2. Press the Menu key.
User Guide Phone
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3. Click Options.
4. Click Call Forwarding.
5. Perform one of the following actions:
• To forward all calls to a call forwarding number, select the Forward All Calls option. Change the Forward All Calls field to a call
forwarding number.
• To forward unanswered calls only, verify that the Forward All Calls field is set to Do Not Forward. Change the If Busy, If No
Reply, and If Not Reachable fields to a call forwarding number.
6. Press the Menu key.
7. Click Save.
To stop forwarding calls, change the Forward All Calls field to Do Not Forward.
Add a call forwarding phone number
To perform this task, your wireless service provider must set up your SIM card or BlackBerry® device for this service.
1. From the Home screen, press the Send key.
2. Press the Menu key.
3. Click Options.
4. Click Call Forwarding.
5. Press the Menu key.
6. Click New Number.
7. Type a phone number.
8. Press the Enter key.
9. Press the Menu key.
10. Click Close.

Change a call forwarding phone number
You can only change call forwarding phone numbers that you have added.
1. From the Home screen, press the Send key.
2. Press the Menu key.
3. Click Options.
4. Click Call Forwarding.
5. Press the Menu key.
6. Click Edit Numbers.
7. Highlight a phone number.
8. Press the Menu key.
9. Click Edit.
10. Change the phone number.
11. Press the Enter key.


Delete a call forwarding phone number
You can only delete call forwarding phone numbers that you have added.
1. From the Home screen, press the Send key.
2. Press the Menu key.
3. Click Options.
4. Click Call Forwarding.
5. Press the Menu key.
6. Click Edit Numbers.
7. Click a phone number.
8. Click Delete.


Delete a call forwarding phone number
You can only delete call forwarding phone numbers that you have added.
1. From the Home screen, press the Send key.
2. Press the Menu key.
3. Click Options.
4. Click Call Forwarding.
5. Press the Menu key.
6. Click Edit Numbers.
7. Click a phone number.
8. Click Delete.