Rhododendrons: Trimming Rhododendron

I am a new home owner and I hired a landscaper to clean up our yard and I fear they have poorly trimmed our bushes. Please let me know what can be done.

The rhododendron have been trimmed underneath with only a few branches left remaining on top (which I know you're supposed to do, but I think the trimming was extreme). These rhododendron are very big, approximately 20 feet high and now nothing is left on the bottom, is this too much trimming? What should I do to keep them healthy?