DARLENEOSEII I'm sorry, but this is the GrapheneOS forum. We help people with GrapheneOS and sometimes with some issues with 3rd party apps or services. It's not that you're not welcome to participate here, it's that this forum probably isn't the ideal place for you to get support for your issue.
The issue here is that RCS requires a very special setup on GrapheneOS for it to work properly since Google apps aren't preinstalled on GrapheneOS. Google Messages is preinstalled on your device, so if you're running into issues with it, then you'd likely be encountering an issue that members here aren't familiar with.
Your RCS issues could be: a carrier issue, a Google app issue, or possibly caused by an issue specific to Samsung devices.
My best suggestion would be for you to try clearing the storage for Google Messages. If you do that, you may lose all of your old messages (not sure). You may also have to set up Google Messages again from scratch, just like you would if your phone was new.
I am not familiar with Samsung devices anymore, but I'd imagine you can try clearing the storage from Settings > Apps > All apps > Google Messages > Storage & cache > Clear storage. Again, to be clear, clearing the storage can delete data, so be sure to back up any data you need from Google Messages before trying that if you choose to try it.