- Your iPhone must be jailbroken. (Zulius provides a guide on jailbreaking and switching carriers for reference )
- Connect your iPhone to the computer and set the carrier as AT&T
- Then once its set up to AT&T (Cingular), again on the computer, set the Visual Voicemail APN to: att.mvno
- Also make sure username and password is blank (Here's a guide that may help in changing the APN)
- Dial your Conditional Call Forwarding activation code to connect (Forwarding instructions can be found here)
**Please note that if you have any issues, we are unable to help troubleshoot. Instead, try posting on the original forum thread here

We are investigating the issue, but it looks to be carrier related, and we're unable to investigate any further. If you are experiencing this issue, please open up a ticket with our Support team (email support@youmail.com), and open up a ticket with your carrier. Our engineers are ready and willing to work with your carrier's engineers to figure out what's going on.