Canceled ATT. Connect to WiFi but no internet on iPhone6

I canceled my ATT network but didn't unlock my phone before traveling. I can connect to the WiFi but I get no data across the phone. How do I fix the iPhone to use just for the WiFI. I can't call the carrier because I am traveling international. I tried my first day to call ATT but without being in the USA they can't text me a verification code. So I am stuck with a phone that has no SIM card/Network. I am hoping to use it with WiFi?

Thanks

Anna