iPhone Find contacts in other apps

[coldwaves]

In my recent call list, it shows a suggested contact name (Maybe: XXX XXX) for numbers that is not in my contact list. I think this suggestions is there because the phone number has occurred in the email I received. I don't want such suggestions so I turned off "Find contacts in other apps" options under the contacts setting. However, even after turning off that options, the "Maybe: XXXXXX" suggestions still occurs below the number in the rennet call list. If I enter that number using the number pad, it still shows the "Maybe: XXX XXX" suggestions.

The description under the "Finding contacts in other apps" says that turning this off will delete any unconfirmed contact suggestions and prevent contact suggestions from appearing in apps". Well, that does not seem to be the case.

So
1) Are the contact suggestion data stored on the iPhone or synced on iCloud?
2) It seems the suggestions data are not deleted right away. I don't know whether the data deletion has to occur under certain conditions. Will plug in the power leave it overnight to see?
3) Any suggestions on how to disable the suggestions?

 

[coldwaves]

I tried a few things myself to explore this issue. Plugging in the phone in power and leave it overnight does not resolve the issue. If I reset all settings, the suggestion still exist. If I signed out of iCloud account, the suggestion still exists. However, if I erase content and rest the iPhone, the suggestion was removed. These seem to suggest that these suggestion data are stored locally on the phone. Once these suggestions were created, it does not appear to be a way to delete it. So far, the only way I find to remove these suggestions is to erase the phone and restore completely.