Is it possible to use data when I am traveling in Canada? or will my phone work only on wifi?
Outside the US, your phone will only work on wifi.
I went up to Montreal this past summer. I had a signal within 5 miles of the border, but beyond that had to rely on wifi. Canadian SIM cards are really expensive for what you get, so I opted to just free wifi it.
I agree with @petej, the Canadian cellular market is about as customer hostile as it gets (at least in the first world). Depending upon which Republic phone you have, pretty much all options are covered here: International Travel with a Republic Phone.
Thanks very much.