i love tethering on my iPhone 3GS, so i have not upgraded past OS 3.0.1
i have used help benm many times to enable tethering and it has worked fine (after setting APN to acds.voicemail )
however after i’ve changed my phone’s password around january, my visual voicemail stopped working all of the sudden.

i’ve tried everything …
- the BlackRa1n 3.1.2 / http://m.peacefulinsanity.com/Tether.mobileconfig (without actually jailbreaking the phone)
- profile / remove
- reset my network settings
- restarted the phone couple of times
… nothing worked, but then … eureka.

i’ve decided to look for the original ATT carrier file 5.5 and then used option / “update” in iTunes 9 to update the carrier file … & it worked like a charm!

[update] – found this good ATT carrier file 6.0 (5.5 that’s hacked to enable tethering) here, which enables you access “cellular data network”