Can't send text from Canada

I'm on the $45 prepaid plan. And am now traveling in Canada. I can make and received calls and also receive text messages. But when I try to send a text message I get this back:
Cricket here! We are sorry but your text message failed. Your destination is not supported from your current location.
Now this is crazy because I'm on att. So where does cricket come in here? Maybe it's because I was with cricket 2 months ago, but then I ported over to Att prepaid, so cricket shouldn't be involved. I spoke to various reps but they couldn't help me and kept on transfering me around. My husband's phone is fine so I tried swapping my sim and his phone but it didn't help. His sim in my phone was fine while my sim in his phone can't send messages. the problem is with my sim or some setting within att. Crazy!