Monkii

If you are there calling local numbers, then it NOT long distance.
You just dial area code + phone number, and only charges airtime

But if you are there calling back to vancouver, then it IS long distance.
You have to dial 1 before area code + phone number, and charges both airtime and long-d

Airtime is basically what's included in your phone package, so if you got unlimited evening and weekends, you still get free airtime during these times.

Monkii

When you are at harrison,

Situation one: You call local harrison number
Only airtime charge according to your monthly plan

Situation two: You call a Vancouver number
Airtime charge according to your monthly plan + long distance within Canada

Situation three: You receive a call
Airtime charge according to your monthly plan + long distance within Canada

Roaming charge is mainly when you travel to US, roaming on another network (ie. Verizon, AT&T, Cingular...), then you have to pay roaming for every minute you call using other company's network.