Thanks for being with Samsung and sharing your concern. We would like to inform you that if you do not want your contacts to get merged then kindly save your contacts only in one storage with Sim card, phone, Google account and after that please follow these steps:-
Go to the device apps > contacts > three dots > contacts to display > select that particular storage.
Go to the device apps > contacts > manage contacts > sync contacts > disable/enable according to the storage. (If saved contacts are in Google account then kindly select only Google account do not sync other accounts).
Go to the device apps > three dots > manage contacts > default storage location > select the location
