Confused about Wi-fi and data plans

I'm a little confused about using Wi-Fi and data plans.

I have a data plan with my carrier (rogers) and an 8220 and not sure how to configure my connections.

When I'm at home should I configure it to use the Wi-fi for phone calls. I DO NOT have talkspot. If I make phone called over Wi-fi without talkspot, do I get charged? thanks for any advice.

From what I have read, using UMA without the Talkspot subscription doesn't cost you anything. However, it will just use your minutes as if you were using EDGE. The only benefit for you doing this is for better signal strength, otherwise it's just Rogers getting your minutes without you even using their network.