If the problem is with your phone, the factory reset has a good chance of solving it. If not, contact your mobile service provider, to carry out some troubleshooting to help resolve the problem from their end.
The Android operating system includes a native visual voicemail that lets you view voicemail messages in text form. If you have an older Android phone or if your service provider doesn’t offer visual voicemail, you can download a third-party app. Select Phone. Select Keypad. Press and hold the number 1. If your voicemail is not set up, select ADD NUMBER. Select Voicemail number. Enter the Voicemail number and select OK. Repeat steps 2-4 to check your voicemail.

6. To listen to the recording, hit Play. If you mess up and want to try again, hit Redo. Save when you're done.
By using the reset network settings, an effectiveoption to solve network related issues, you can fix allthese problems by simply resetting the networksettings of your iPhone as it will clear all the networksettings, current cellular network settings, saved Wi-Finetwork settings, Wi-Fi passwords, and VPNsettings How do you reset your voicemail greeting? From the Home screen, tap the Phone icon . Tap Voicemail then tap Greeting (upper-left). Greeting islocated in the top-left corner of screen. Tap Custom to record a greeting. Enabled when a checkmark ispresent. Tap Record to begin recording the custom greeting message. Tap Stop to end recording then tap Save. How do you change voicemail settings on iPhone? Go to the Phone app, then tap the Voicemail tab. Tap Set Up Now. Create a voicemail password, then tap Done. Enter your password again to confirm it, then tap Done. Select Custom or Default. If you choose Custom, you can recorda new greeting. Tap Done to save your greeting.