Answered question
I order a SIM card and 2 other by mistake I want to cancel my order for the 3 SIM card???
I don't think you can, try by chat. At least they are not expensive, réelle on Kijiji or use one as a burner and test plan before porting your number.
Other answers
You can do a charge-back if you ordered using a credit-card. Just throwing another option out there.
Put on kijiji, I'm sure someone will take it.