There is another method to set call forwarding times, however, it requires use of two (generally) standard GSM codes:
*#61# and CALL/SEND to determine the forwarding number for voice calls, and
61Forwarding Phone Number
11Time# (in increments of 5 seconds to a maximum of 30 seconds) and press CALL/SEND. _I always use the entire Forwarding Phone Number string as it appears in the *#61# result screen, including the prefacing 1 at the beginning of the Number; I live in the US and occasionally travel to Canada or Mexico._
+_A caveat_+: ATTWS has related to me a few times the their time counter starts if the time ringing goes longer than 30 seconds - I've never set my forwarding for longer than 30 seconds and had ATTWS charge me for a missed call.
ATTWS reset my voice mail time from 30 seconds to 20 seconds and I was missing a few calls because I just wasn't quick enough. I used the above two code strings to change my answer time in about one minute - QED. A quick way to get through to a real person with ATTWS CS is to dial "0" after you enter in your phone number a couple of times at the prompts - sometimes doing so gets me a real person in a minute or two.
There are other codes for data, fax, call waiting, etc. - all of those "buttons" you tap are really just sending GSM codes to the network. And for any gomers reading this post that want to be a pain, yes, GSM codes generally are supported on the WCDMA network. It's up to the wireless provider to support and/or block the codes.