Welcome to Three community
@Betty1 I assume you are not talkin about MMS(where you are charged small fortune)
If you are talking about using the built in sms/messaging app that comes on your phone behaving almost like whatsapp/telegram/signal... where you can send pictures, emojis also see dlivery and read receipsts, such is only supported if both ends (sender and receiver) have RCS (Rich Communication Services) enabled.
on android, to enable RCS messaging
Ensure that Google Messages or Samsung Messages is the default messaging app
Open the messaging app
Go to Settings
Look for Chat Features or RCS
