International call, I'm in China now, and I want to contact a friend in Canada. What should I put before the number when I send a text message to make a phone call?

The most convenient way is to use skype~ to call landlines, mobile phones, send short messages, and leave messages to each other when you are away. You two can use the same account, and it will be cheaper for her to run in Canada (renting a global service costs only 12 Canadian dollars per month), and then you can use this account to call each other's landline or mobile phone or send text messages on your computer at the same time, which is the most convenient and cheapest I have ever used, because there are computers everywhere in Canada, and one computer even saves telephone charges.

Good luck!