When I use Bixby as my assistant via voice activation to text a person by saying Hi Bixby, the text message is sent as an MMS message to the recipient instead of being sent as an RCS message. I have RCS setup and it is working properly. For example, if I just open j the messages app and type a text and hit send, the n sage gets sent as an RCS message to the recipient as it should. The issue is with Bixby. How do I fix that? For further proof this this is a Bixby issue, when the recipient replies back to my text is their reply is RCS. I am using the Google messages app which came pre-installed on my brand new Galaxy s25 ultra. As a matter of fact the Samsung version is not even installed. The phone is an unlocked version (USA version) and this is the factory installed messages app.
Open the Galaxy Store app, and you can download and install Samsung messenger and try that instead. IIRC, Samsung has converted all of it messaging to using the RCS chat mode instead of MMS.
