Originally Posted by
Dubai Stu
I live within a few minutes of the US/Canadian border and cross frequently. My problem with ATT was that my phone would try to hold a weak ATT signal in the border region and I finally got ATT to push to my iPhone an update which would allow me to manually force my phone to a US or Canadian carrier even when a US signal was detected. I spent hours on the phone arguing with people to get it and customer supported originally denied it existed. I had to remain firm, polite, and a little bull headed to get the update through.
AT&T carrier unlocked your iPhone. We had a similar problem with one iPhone not sending texts in Vancouver with tier 2 tech pushing the change to the phones. Carrier unlocking is the only method to manually select the carrier. All US cell companies except for Verizon will carrier lock the phones sold.