For Apple users:
Go to Settings and tap Notifications.
Select YesRef under Notification Style.
Under Alerts, choose the alert style that you want. If you turn on Allow Notifications, choose when you want the notifications delivered – immediately or in the scheduled notification summary.
For Andriod users:
Open your phone's Settings app
Tap Apps and notifications. Notifications.
Under Recently sent, tap YesRef
Tap a type of notification.
Choose your options: Choose Alerting or Silent. To see a banner for alerting notifications when your phone is unlocked, turn on Pop on screen.