To force close Phone, on iPhone X and later swipe up until you see the apps in task view, then swipe up again on Phone. On iPhone 8 and earlier double press the home button, then swipe up on Phone. You will see all the open app cards.
Try to avoid casual salutations like, “Hi” or “Hey” if this is your first time calling someone. Your introduction should be one or two sentences tops. From there you can move on to the body.

I like to say my phone number very early so the person can hear it again quickly by starting the message over and does not have to listen to your entire message again to hear the number. But do repeat your telephone number at the end of the message at least once and speak very s-l-o-w-l-y so the person can write it down as they listen. If you don't get a response to your first voicemail, don't hesitate to record a similar message once a week for two or three weeks. This sounds a bit excessive, but my experience has been that if there is even the slightest chance of meeting someone now or even in the near future, this kind of message will get their attention.
“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.”