OnePlus
Contact List Name Format auf OnePlus
OnePlus stores a contact's first and last name as two separate fields, but the Contacts app only ever shows one combined string in the list. Which part comes first in that string is decided by a single system setting called Name format, not by how you typed the name when you saved the entry.
This setting applies to every contact at once, including entries synced from your Google account or copied from a SIM card. It only changes how the app renders the name for browsing and searching, the underlying first name and last name fields stay untouched.
To switch it, open Contacts ➔ Open the menu ➔ Open the Settings ➔ Tap on Name format, then pick First name first or Last name first.
If you actually want a different alphabetical sort order rather than a different display order, look for a separate Sort by option in the same Settings screen instead. Changing Name format alone will not reorder the list alphabetically.
Contacts that were imported with a single combined name field, instead of separate first and last name fields, may ignore this setting because there is no split data to reorder.