You have a 5 sided nut. Called a Penta-Nut, it's original intentions was to have only trained people undo the rim.
It uses a specialty impact socket to remove. You can then take a 1/2" impact wrench to undo them.
Unfortunately, you're stuck with two options...well, mabye 3.
1) Go to the dealer. If you do, they need to replace the nuts with standard 6 sided nuts.
2) Order a Penta-Nut socket from
www.bluehummer.com. Order 6 sided nuts to go with it.
3) Find someone in the area that has one. Order 6 sided nuts as well.
I will say that if you undo this on your own - be careful. I've seen accidents with rims when someone doesn't deflate it properly and completely.
Now - you also have to be sure that you don't have a runflat inside. If you have a runflat inside, you also need a runflat compressor, which is a 4" wide crank operated ratchet strap. That's another dangerous item to work on.
Now you know why the tire shop says that they won't work on them.