what's the meaning for We do not ship to P.O. boxes

Pretty self-explantary. Means you need a street address that matches your credit card billing address.

I suggest editing your message and removing your street address, as this forum is searchable by everyone on the Internet.

If you want a phone from Canada, you need to either go to Canada and buy it in person, or have it shipped to a Canadian street address. The Canada store only ships within Canada (and the USA store only ships within the USA), and either store will require payment with a credit card with a billing address in the same country as the store.