I tend to think it's your own fault. But I'm ASSuming a few things.

Here is what I do BEFORE ordering an oversized item from someone new:
CALL THEM .... ON THE TELEPHONE

Talk to them and tell them EXACTLY what you want. Tell them you CANNOT accept delivery of the product if they cut it down or resize it in any fashion.

Be prepared to pay for the shipping.

I do think they rushed your order out the door without consulting you on the size and shipping issues.

But I also think you had the initial burden of making sure they would actually ship the item you ordered without cutting it apart. Thats your own fault.

The fact that they did cut the product without asking you first is pretty stupid on their part.

I'd personally call it a wash at this point and follow w8ye's advice. Don't order from them again.