Thanks again for all the replies. Until I figure out which monthly plan I want, I am using AT&T Go Phone - which is terrible. I have used up $35 of credit in 6 days but at least know more about what my calling habits are.

~ 300 minutes a month in total including Canada (about 100 nights and 50 weekends + 150 regular)
~ 100 texts
~ voicemail, caller ID
~ about 100 minutes a month to Canada (75 nights and weekends + 25 regular)
~ will roam to Canada about once a month.

I think I will choose the T-Mobile plan; the clerk today told me about FlexPay but I don't really understand it. Is it just a monthly plan without a contract when you pay beforehand?

I don't mind leaving the deposit ($500 ) for a monthly plan but with the way the US$ is going, when I convert the $500 back to CAD$ after 12 months I will have probably lost quite a bit of money.

Also - if I am not on a contract can I "skip" months? i.e. have my plan from Sept-Jun only?

Thanks!