If you are unable to access voicemail on your iPhone – which means you're getting the “Visual Voicemail Is Unavailable Error” – it is most probably a network issue. Before reaching the voicemail number to check your voicemail through a phonecall (which, I needn't say, is a pain in the back), you might want to make sure your network works fine. In about 90% of the cases, once you get to a point where the signal is strong and the network is working fine, your voicemails should be instantly available.
The trick in fixing the Visual Voicemail Unavailable Error is to reset your network. Before this, though, you should try to fix the network. We've got a variety of ways to fix network problems.
1). Airplay Mode Fix
Turning ON the Airplane mode and then after about 10-20 seconds, turning it OFF again is a well-known (and pretty old) trick to fix 3G, 4G or LTE network settings. Like I said, since it's most probably an issue with your 3G/LTE setting, the fix might be to switch off all network ports and then restart them. That's what you do here.
- Go to Settings → and turn ON Airplane Mode
- After about 20 seconds, turn it back OFF and wait for a while before trying to fetch Voicemails again.
Before you head to check the Voicemail from the Phone app, check mail or open a website to see if your network is working fine.
If the above method doesn't work, you might as well try to reboot your iPhone. This effectively refreshes all connections and in the process, might fix the network problem.
On a non-jailbroken iPhone, you're going to do this:
- Hold the Power button and slide to power off.
- Power on again as usual.
3). Reset Network Settings
If nothing works, don't loose hope. There are two more options remaining although the last one isn't really an “option.”
For the 3rd method, you're going to reset network settings. To do this:
- Go to Settings → General → Reset → Reset Network Settings
Note that when you do this method, you're going to lose Wifi passwords but this method has a strong chance of getting your network issues fixed (provided you're not living in a remote area where the reception is bad).
4). And if all else fails, unfortunately, call up the voicemail number and retrieve them. Sure, it sucks but when there's no other go, you know what they say about the mountain and Mohammad.