Your AT&T VoiceMail Service access number is: 1-888-288-8893. When calling from home, if prompted, enter your password followed by #. If you are not calling from home, you will be prompted to enter your 10-digit telephone number followed by your password, then just follow the system prompts. From any Home screen, tap Phone. Touch and hold 1 or dial 123 and tap Call, or tap the Voicemail icon to call voicemail.
Unfortunately, there’s no built-in button in your iPhone’s phone app for recording calls. Instead, you’ll have to use a third-party app or service or use a clever workaround.

If a phone rings once and then goes to voicemail or rings only briefly, it You can't definitively know the cause of a phone barely ringing and going to voicemail because neither a phone company nor the phone's operating system provider will tell you if your phone number is blocked.
“Hello! You’ve reached the voicemail of [your name], [your job title]. I’m currently either away from my desk or on the other line. Please leave your name, telephone number, and a short message after the beep, and I’ll be sure to get back to you as soon as I’m available.” Press and hold the 1 key to access the voicemail system. When you hear the recorded message, press the # key to bring you to the system menu. Press 4, for the Personal Options followed by 2 for Personal Greeting. Follow the prompts to record, listen to, re-record and save your greeting. How do I change my voicemail number on Samsung Galaxy s8? Find “Voicemail number” Press Phone. Press the menu icon. Press Settings. Press Voicemail settings. Press Voicemail number. Save voicemail number. Key in +61414121121 and press OK. +61414121121. Return to the home screen. Press the Home key to return to the home screen. Dial voicemail: Press and then hold on the envelope icon displayed on the main screen. Enter Your Accounts Password: Enter the password if prompted. Delete voicemail: Tap 7 on any voicemail and it will be deleted successfully. Open the dial pad on the device. Open the application drawer and scroll through to find the Phone app. Dial Voicemail. Tapping the number 1 and then hitting the green phone icon at the bottom should call Voicemail. Enter a password (if there is one). Skip through messages. Delete a voicemail. Log into Google Voice. Click on the gear icon. Select “Settings” from the menu options. Click the “Voicemail & Text” button. Click “Record New Greeting” in the Voicemail Greeting section. Enter the name for the greeting you are going to record. Select forwarding phones. Click “Connect.”