If you have a visual voicemail applications installed on your Galaxy S21, you can alternately use that app to record and set a greeting instead.
Step 1 – Set your PIN – this protects your mailbox from eavesdroppers. Log on to your mailbox. Dial 6 7 for mailbox options. Dial 7 for security code. The phone system will guide you through replacing your 4-digit security code. Step 2 – Record your name. Callers may hear your recorded name before leaving you a message.

Select the Voicemail tab. Below "When callers reach my voicemail, play my," select one of the following types of voicemail greetings: System Greeting - Plays a system generated message that utilizes your recorded name and is the default setting for all new users. Personal Greeting - Plays a custom message that you record using a phone.
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.