yes, import-export of contacts or products requires a clear approach to update exactly the data that is required.
The column by which you need to search for a contact must be specified. The best - by ID. That is, you download, for example, an Excel file with ID, surname, first name, patronymic. When importing - also be sure to specify the binding of speakers (screen, phone replace with PIP)
https://img.crm-onebox.com//media/61/20/6120a8ce09df01a3d387c7ebcea9a6ae.pngBe sure to check the report file in the mail after the update, it should be Updated: 1xx (the number of updated contacts)