How do I delete all messages in my iCloud ( my messages app is not on in my iCloud ) Yet they are showing up in my CarPlay screen in my vehicle from 2018 & 2019 ! # FRUSTRATED

Anyone ever experience this?? I can touch screen and say “ test message do not respond “ unplug usb cord “ that single person message shows up on iPhone XR & I delete it off my iPhone , plug back into usb cord & Carplay & that single person message is deleted But group text messages from 18 & 19 - Siri responds “ I’m no longer a member of group message “ and can’t delete these. In addition there’s so many “ single person “ text messages that keeps popping up ( screen shows 10 at one time and once you delete one another pops up ! ).

There’s got to be away to delete EVERY MESSAGE in my iPhone iCloud without having to do all of this- without buying a new iPhone & if I do , I’ll have to use the same Apple ID in order to download all my apps and especially my notes, books , passwords - where I store my most important information- especially “ books “ where I keep caselaw ( since I’m an attorney)