You can leave a note for OpenStreetMap (OSM) contributors with the description of the issue. Tap the "Edit place" button on the place page → scroll down to the → bottom → leave your comment in "Send a note to OSM moderators" section or tap "Place does not exist" → tap the checkmark in the upper right corner (Android) or Save (iOS).
Alternatively, you can leave a note for OSM contributors directly at OpenStreetMap web site: find and zoom in to the necessary location, click on "Add a note to the map" button and leave the description about necessary changes on the map. In this case it’s necessary to wait till someone of OSM contributors edit the map in accordance with your comments.
Or you can edit the map yourself at OSM. You can learn more about editing OSM maps here.
Note: if you just added the place and haven't signed in OpenStreetMap profile, then tap the place on the map, pull up the white banner and tap "Edit Place". Scroll the page down and select "Delete".