Have you properly configured the APN settings? And do you still have data left on your plan? Given the wording of your post I assume you are a new customer so it is probably a configuration issue, but it's worth mentioning that I have had a similar s...
Most likely this has to do with the cell network coverage in your area. Calls use 3G, so even if you have a good signal on LTE for data it is possible that you have poor coverage on 3G. You can try to force your phone onto 3G in the settings. This sh...
The US add-ons are fully separate from your normal plan. Data and minutes are counted separately than your normal Canadian counts. You can choose your add-on according to your needs for your trip.
If you replied to the message, then it will change your plan on your renewal date. Unless that date has passed, you will still be on the old plan. I switched over the same way, and didn't see anything on my account after replying to the text. However...
Self serve has been acting up lately with changes to service like this. Try to clear your cache and try again, or use a different browser/device than usual. Odds are the data really is on your account, but just isn't showing. If all else fails, a sup...