You can disable notifications and switch accounts in your Rakuten extension Settings.
To open the Settings menu:
If you want to turn off the Cash Back notification you see when you visit a site, check the box that says Do not display Activation Hover on these sites. Enter the URLs of sites where you want to turn off Cash Back notifications. When you’re done, select Save.
If multiple people use your device and you need to switch accounts, select Not You? next to your email address to sign out. Then sign in with another account.