Hi
The following steps may help:
On your iPhone, in the Contacts app, check that there is a single contact card for each of your contacts and that each card contains that contact's full name and phone number.
Having made any changes in the Contacts app, on your iPhone, in the Watch app, go to: My Watch > General > Reset > tap again on Reset Sync Data.
- Nothing will seem to happen, but the process will run in the background / invisibly to you, so allow some time afterwards for it to complete.
Restart both your iPhone and your Apple Watch, turning both off together, then restarting your iPhone first: