kartonage
Facebook may not use OpenStreetMap data alone which is the reason their data may be bad. They might use Mapbox, they might not, either way they will have to fix it on their side. They may also send you here because it's easier for them to send you away. It's their service that gives your problems and there is nothing that directly could be fixed here (check Nominatim for accuracy of search queries for the city in question). If you believe it's still an error on OSM side please contact data@openstreetmap.org with details on why Facebook support things it's an error on OSM side etc. Thanks.