If you’re in a group with someone, you can mention them in a message by typing the “@” symbol and selecting the contact’s name from the list. When you mention someone, they will see an “@” symbol notification in their chats list next to an unread message.
Note: Mentioning someone in a group will override any mute notifications that contact has set for the group, unless they've muted your individual chat.
You'll see an “@” symbol notification in your chats list next to an unread message if you’ve been @ mentioned or someone has replied to your message. When you tap into that chat, you can quickly catch up on messages you were mentioned in or replied to by tapping the “@” button that appears in the bottom corner of the group.