Incoming Call showing double name

If you have the same contacts stored in multiple email accounts and if you add these accounts in an iPhone it may display as duplicates.

Unlike some Android devices, contacts are neither stored locally on an iPhone nor in SIM. They are synced to an email account that you had Google, iCloud, AOL, Exchange, Outlook, Yahoo or any Other

Do you have the same phone number associated with two contacts?

Here is a resource that may help.

• Add and use contact information on iPhone - Apple Support