Coolpad mobile phone receives 10086 phone bill reminder service SMS at around 23:30 every day.

You don't have to worry about that. If it is custom machine, it is mandatory to check the phone bill at a fixed point. If it weren't for custom machine, it's possible that you would send a text message to open a fixed-point phone bill inquiry service. This has nothing to do with your mobile phone, but this service seems to be five yuan a month and can be cancelled manually.