Hi @J777, let me see if I can give you some information here.
Rich Communication Services (RCS) is a messaging standard designed to replace SMS. It is also marketed as Advanced Messaging, Advanced Communications, joyn, Message+, and SMS+. RCS is provided by mobile operators, and it's supported by Android devices using the Android Messages app from Google.
With the RCS standard, a number of functionalities are added to the messaging application on your device. For example, RCS allows you to attach high-resolution pictures, videos and audio to your messages, and enables you to chat with other RCS users. If the person that receives the message doesn't have RCS support, the message is converted into an SMS/MMS message.
Xperia C4 does not have Android Messages as standard and can't use this unfortunately.