When clicking on the Voicemail button, instead of hitting the Apple Visual Voicemail, the phone placed a call to Voicemail. When the icon is tapped, instead of showing the visual voicemail screen phone would place a call to voicemail. Visual voicemail appears to be functioning, nothing denotes otherwise. Panic Not! Calling Apple Tech team will reveal that similar issues have been faced by several hundreds of iPhone users.
Resolve iPhone Visual Voicemail Problem
Please run the below diagnostics before confirming the Visual Voicemail issue
Upgrade latest iOS
Use iTunes to revise your iPhone to the latest edition of iOS.
Ensure you have good cellular network connection. You can verify it by making and receiving phone calls.
Voice Mailbox Setup
Now try dialing your phone number from your iPhone to make sure your voice mailbox is set up properly. If this fails try resetting your network settings by tapping Settings > General > Reset > Reset Network Settings.
If the issue is still not resolved, then there is a possibility that the issue is not specific to your device. This could be due to the way your account has been set with your carrier.
Resetting your Voicemail Pin
Try resetting your voicemail pin with your carrier and then try activating the same through your phone.
For instance: If your carrier is AT&T then
login to the AT&T website, choose your model. Choose to reset the voicemail option appearing on the column on the right hand side. Select submit if the website prompts you to reset the pin/password. One should receive a text saying that the password has been reset to your phone number in a text message.
Please note that the new iPhones are required to receive a voicemail or two for the visual voice mail to become active.
Call yourself from your phone. Post one ring, you’ll hear your voicemail. Leave yourself a communication. Verify the voicemail by clicking the voicemail icon. Check if it gives you the password/pin prompt If not prompted, make a few more tries. It will prompt you with the option.
(NOTE: The voicemail password is the pin with your Carrier, and NOT the password for the Apple ID. Once you enter the carrier PIN, return to the voicemail tab and the visual voicemail can be seen online.
If all fails, then in most cases, restoring the iPhone option works. At times you may encounter an error. In this case when trying to restore your phone in iTunes, you may
see the following message followed by an error code 1601 or 1602: The iphone could not be restored. An unknown error occurred.
Solution: Completely remove iTunes and Apple Mobile Device support and then reinstall iTunes 7.5 or higher to reset your voice mail and you are good to go.