In order to take advantage of Extended Coverage, you technically don’t need to have Data Roaming on. With Data Roaming off you will still have access to Extended Coverage networks for Voice (Phone Calls) and Text Services.
If you are looking to use Data Services on an Extended Coverage network, you will need to have Data Roaming on.
In regards to the incurring Roam like Home charges, Rogers has introduced a new Accidental Roaming Policy. The entire US/Canadian border (up to 2 kilometers in radius) is covered to make sure you will not be charged roaming if connected to a US tower when you are in Canada.
Also, you can manually set your network to Rogers if you prefer to not have it switch to AT&T. Extended Networks will show up as Rogers-EXT.
Keep in mind that we are working with US operators to make sure all towers located along the border are identified, so we can ensure to charge domestic rates versus roaming rates. However, when any new towers are created we are not always notified right away, so your phone may connect to a tower that we have not yet flagged.
On another note, you will still receive a text message that you are roaming. We are working to get this fixed.