As I mentioned earlier, one of the common reasons why an iPhone won’t play voicemails is because the Phone app isn’t working properly. Closing and reopening the Phone app allows it to “shut down” and start again, which can sometimes fix a software glitch.
If you’ve already created a custom voicemail on your iPhone, you can tap Play to see how your voicemail sounds. If you’re interested in creating a new message, tap the Custom button. From here, you can start recording your message by tapping Record and tapping Stop whenever you’re finished. Once you’re finished recording, tap on Play to make sure the message comes across as you’d like and hit Save (in the upper right) to save it as your voicemail.

There are two steps you have to do before you can use voicemail on your phone. The first is that you have to add a voicemail number. This number varies by country and also your service provider. If you’e use AT&T, you can follow AT&T Galaxy S21 voicemail setting. Open the “Phone” app. Tap the 3 dots on the top right. Tap “Settings“. Tap “Voicemail“. Tap “Voicemail Settings“. Take note of the green number below “Voicemail number“. Go back to the dialer and enter the number from Step 6 (including the *). Press the green phone button. The voicemail number has been set. Return to the Start screen.
Closing out of your apps is like turning your iPhone off and back on — it gives your apps a fresh start. If one of the apps that you have open crashes in the background, it may prevent other apps you have open from functioning properly. It can be difficult to identify which specific app or apps are malfunctioning, so we'll close them all to save time. Double-press the Home button to view the apps your currently have open. Use your finger to swipe up on the apps to close them. You'll know all your apps are closed when you only see a preview of your lock screen.