Delete FDN (Fixed dialling numbers) with contentResolver

Question

I would like to manipulate the FDN (Fixed Dialing Numbers) list from my application. The insert and query functions work fine, but deleting simply doesn't work. The function returns that the number of deleted rows is 1, but the actual deletion never occurs. No exception is thrown. I have both READ and WRITE CONTACTS permissions in my app. The function in question is:

public final int delete(@RequiresPermission.Write @NonNull Uri url, @Nullable String where,
            @Nullable String[] selectionArgs)

What I've tried:

Both where and selectionArgs are provided. Only where is provided. Neither is provided, resulting in a NullPointerException.

The example where clause: 'number='132413' AND tag='exp' AND pin2='141234'

Another example where: "number=? AND tag=? and pin2=" + selectionArgs with the values.