Sent in my Nikon lens for service, came back with dust on the inside?

I sent in my Nikon lens because the front element fell out. I got my lens back, but there are a lot of dust particles on the inside of the lens, one of them is fairly large and visible even in some shots. Has anyone had that experience before? Send it back again? What's the guarantee they will clean it properly this time?

Added (1). I did sent it to Nikon

Did you in fact pack the camera yourself and send it to Nikon or did a camera shop do this and maybe used a "repair shop" instead of Nikon?

I would say what probably happened is that while the front element was out dust had a chance to get inside and did. Nikon probably didn't clean that out when they fixed it. To get that done you'll have to send it back or go to a shop. In this case you may have to pay to fix it.

Understand that if you do have to pay for it, it may be just as cheap to replace the lens.

Get on the phone, and complain like hell! It's simply not acceptable that a lens that has been serviced due to the front element falling out is returned in such a condition. This is a fault with the service centre, you should not have to pay again for further service, and you should not even have to pay for the carriage this time either. If you have issues then get whatever consumer protection agencies exist in your area involved.

I'm a Brit and I thought we were supposed to be apathetic in regards to poor service!