iPhone does not work in Canada

[Galethewhale]

I inherited my daughter's iPhone 4S just a few weeks ago, upgrading myself from a Basic phone.  I often travel to Canada to visit family, and we have a phone plan that includes Canadian service for our whole family.  There are two iPhone 4s's in our family.  My son's works fine in Canada, and this phone stops service as soon as you hit the border.  Any idea what is wrong?  Is it a locked SIM card?  Do I need a different SIM card for Canadian service.  By the way, this phone used to work fine in Canada, but seems to have stopped working.

[#2 · Accepted solution]

Make sure cellular and data roaming is set to on in your device settings.

Should work fine then.

Good Luck