My question is I have a canadian app that provides me with a canadian phone number that uses data or wifi. I also have a travel sim card so the question is if I forward my telus number to my app number and change to my travel sim card will I be charged long distance rates while in the US. The app will work as I have used it many times , I will be forwarding an assigned telus number to my app phone number while using a travel sim .card
If it's a local call, forwarding your TELUS cell to this other phone number shouldn't be a problem. You will however get billed for forwarding minutes and it rates varies depending on your rateplan. if it's not a local call, you will be charged long distance regardless if you're roaming in the US or in Canada.
if you use a travel simcard in the US and (assuming you will be using local carrier data while roaming), your number is forwarded to the app's number, you shouldn't be charged long distance or roaming.
As Chuck81 has explained so long as your plan includes Call Forwarding, and the number being forwarded to is local, then there are no additional charges. However if your plan does not include Call Forwarding, you can add it as an extra add-on for $3/ month and remove it whenever you would like.