Canadian shopping at Yesstyle.com and Import duties?

It was my first order at Yesstyle. I bought clothes worth roughly at $170 CAD and to my surprise they charged me $49.99 CAD for the import duties. I live in Alberta where we only pay 5% GST for the goods that we buy locally. I'm really not happy and wondering if anyone has the same problem, if so, please tell me how much they charged you for the stuff you bought and how much was your stuff worth..Thank you.