Sounds like you should make future purchases of it through a different broker. I have purchased SDRL through TDAmeritrade, Scottrade, and Interactive Brokers with no additional fees being charged. Goodluck.
I've bought SDRL a couple of times in my Vanguard account and paid only the $7 commission. NATDF and other foreign-listed stocks do require you to phone them and will cost an additional $50, but buying SDRL online should not.