Yes. I had the same problem and with this it was fixed. Here's a link if you want to give it a try.
https://www.apkmirror.com/apk/google-inc/google-assistant/google-assistant-0-1-187945513-release/
Maybe try upgrading to 4.4.070? Hail Hydra.
https://www.apkmirror.com/apk/google-inc/messenger-google-inc/messenger-google-inc-4-4-070-release/
It sounds like you need to deactivate Hangouts. To do this:
The number in the app is likely the same one as on your SIM card - you can check what you SIM card shows using https://play.google.com/store/apps/details?id=com.gsmdev.simcard this app. More than likely you have ported your number from another network and you were assigned a temporary number for 48 hours which is the number on the SIM card.
Well just to check, I've just installed Textra ( https://play.google.com/store/apps/details?id=com.textra ) from the Play store and switched to using it as the default app, all my previous RCS messages are instantly visible - including any media that was sent with messages. I don't send MMS messages ever, because they cost 55p a message in the UK. They might well be working on an RCS message store - because right now they are clearly being stored in the Android SMS message store, and that's the internal storage on the phone, which could fill up very quickly if people are taking advantage of the ability to send large media with RCS. Working on a proper message store, would allow RCS media to be stored on an SD card instead of filling up the phone storage. Especially since messages is lacking the functionality of other messaging apps - purging older messages.