I keep getting spam messages when I change my calling card.

Click Settings -iCloud, and then turn off all options and functions in iCloud that don't need to be synchronized with each other. The automatic download function should also be turned off. Click Settings -iTunes Store and AppStore, and the function of automatically downloading software should also be turned off. Set-message -iMessage, and turn off the function of information synchronization, so that messages will not be synchronized with each other.

It is best not to share an ID account, otherwise important data files cannot be backed up independently, and once lost, they cannot be retrieved.

Also, even if you share a file, don't turn on all iCloud synchronization options, otherwise data and information will be synchronized with each other, resulting in confusion of mobile phone information.