Text-based conversations between users with searchable history in Microsoft Teams Free
Hello
Does your friend have a Microsoft account already? If so, in Teams, you can simply start a new chat and add your friend's Microsoft account to start chatting. Make sure your friend installs the Microsoft Teams app on their phone.
If your friend doesn't have a Microsoft account, you can still type their email address into the chat invite field, instead of adding them, it will show "Invite" for you to send a link to their email address, so they can sign up for a Microsoft account and install Teams to join you.