Check the payment instructions on the Embassy of Canada's website for your country (usually found by clicking "Visas and Immigration" on the bar on the left. Then check toward the bottom for "Practical Information; * Fees and Payment Options"). It has detailed country-specific instructions on alternate payment options.
Faranak,
To pay the FSW processing fee from Iran, you have the following alternatives:
1. Get the Credit card details of someone you know.
2. Ask a friend or relative abroad to get you the money order as instructed by CIC and then send the original money order to you via courier mail.
3. I have heard some money exchange agencies ("Sarafi") would get you the money order for you, but they will charge an additional amount of about $150 for that which seems really unfair.