While in Canada I've purchased Tracfone airtime "cards" on-line from Walmart.com. The PIN number is emailed to you. But I still don't know if adding the card via Tracfone's web site is sufficient to keep the account active when the phone has no signal or whether the time/minutes also have to appear on the phone itself, which, of course, is not possible if the phone has no service signal.
Last I heard, Tracfone would not mail a new SIM card to a Canadian address. Maybe this has changed.
Also, I understood that all accumulated minutes were lost if the phone expired and a new SIM card was needed. It would be nice if this were not the case and some on this thread are reporting otherwise. As suggested, maybe a phone call to Tracfone can address.
Tracfone's CDMA phones worked in Canada (not anymore?) but Tracfone would cut off the service if they became aware of such use. Some people apparently got away with limited use. I believe Tracfones sold now in Walmart stores are all GSM phones with SIM cards and they do not work in Canada.