contacts duplicating

See this > If you see duplicate contacts after setting up iCloud Contacts - Apple Support

This is a common issue when using multiple accounts. Be sure that all new contacts created are saved to iCloud, rather than local or alternate network accounts. One way to test this is by opening up contacts on your device, and hiding certain accounts under the "groups" section. This will allow you to see where the duplicates are stored. If you go into settings > contacts > default account, make sure that the same account is selected across all your devices. When duplicates do appear, you will often have to delete them manually, although the process is a bit easier on MacOS.