I have problems sending and receiving text messages on my OPPO Reno4 Pro 5G

Press the message icon.

Press Start chat.

Press the search field and key in the first letters of the recipient's name.

Press the required contact.

Press the SIM icon.

Press the required SIM.

Press the text input field and write the text for your text message.

Press the send icon when you've finished your text message.

Press the Home key to return to the home screen.