You can merge locations into one listing in two (2) ways:
If the addresses match:
Contact Google to merge both locations.
If the addresses do not match:
One solution is to mark the location as a duplicate or mark it as permanently closed.
- Go to Google Maps and search for the location you want to merge to your listing.
- Click the 'Suggest an edit' option.
- Click 'Close or remove'.
- Choose 'Permanently closed' or 'Duplicate of another place'.
- Once done, click Send.