Edit permalink for certain pages

I agree with @Milo it would be easiest to do it by having the Services Page as your top level page (parent) and then declare other pages as the Services pages’ children.

You can do this on the page editing area in the WP admin area.

Try not to mess with the permalinks as that can have crazy consequences on things working as they should. If that solution doesn’t work out, create a custom post type of services. That way anything in that custom post type will be under the services type!

There are a variety of plugins to help with this. You could also write your own plugin to do this too!