Database structure for categories, sub-categories, and services

I am using Laravel 5.5 and MySql. I cannot figure out how to relate Categories, and Sub Categories to Services without adding a subCategoryID column to the Services table.

Currently this is my table structure

Service_Categories

id, name
1, Legal Services
2, Personal Drivers

Service_Sub_Categories

id, ServiceCategoryID, name
1, 1, US Legal Services
2, 1, Europe Legal Services
3, 1, Canada Legal Services

Services

id, serviceCategoryID, name
1, 1, US Legal Services Comapny INC
2, 1, Canada Legal Services Company INC
3, 2, JSY Personal Drivers
4, 2, XYZ Personal Drivers

One service must have at least 1 Service Category but it can also have 0 or more Sub-Categories

As you can see, Personal Drivers has no sub-category, but Legal Services has many Sub-Categories. When a user selects "US Legal Services" I only want to pull those up. I could easily add a subCategoryID column to the Services table but in the future I may have sub-sub-categories. What is the best way to structure my tables?

via Chebli Mohamed