I would never pay the daily rates Tharp Canadian phone companies charge. I am in the US several months a year and have never paid to use my phone. It goes on airplane mode before crossing the border and stays that way until I am back in Canada. iMessages can be sent to iPhones when connected to wifi and you can communicate with Messenger, Skype, WhatsApp, etc while connected to wifi. If you are concerned about security while using public wifi then get a VPN.