Sorry to hear that!I've done that - it doesn't help.
I disconnected my car from the Octopus app a week ago, so I no longer have any devices configured at Octopus. I'm still getting the unwanted messages, and they prevent me from using the myBMW app properly (because any schedule I set in the myBMW app simply gets overwritten every 4 hours).
I updated the MyBMW app today but haven't had a chance to try it yet, hopefully this might improve things!