I had a similar issue when I traveled to Japan and China.
I'm a customer of T-mobile, and yes I did in fact use internet on my android phone (had no idea how much it was going to cost me). But even with almost full usage, my bill came out to $1,300 (Data and voice).
I called T-mobile and asked them what the charges is, and after they explained its mainly my data charge lied to them that I never used my data there. The whole time I was being nice and persistent, and the person on the other line agreed that since it's a smartphone it uses data connection automatically, and spoke to the higher ups to revoke the high charge (still had to pay for voice but I was happy with data fee out of the way).
So call AT&T, be nice but also be persistent, and tell them your story in good faith. That it is your father who had the phone and he has no idea how to use the internet yet. Also mention that you think all the data usage is the iPhone itself connecting to update itself (update time and what not). You can say that these charges were never explained to you.
If all fails, go to the store. You being there in person is going to be harder than the line "dropping" if you were to call.
I called T-mobile and asked them what the charges is, and after they explained its mainly my data charge lied to them that I never used my data there. The whole time I was being nice and persistent, and the person on the other line agreed that since it's a smartphone it uses data connection automatically, and spoke to the higher ups to revoke the high charge (still had to pay for voice but I was happy with data fee out of the way).
So call AT&T, be nice but also be persistent, and tell them your story in good faith. That it is your father who had the phone and he has no idea how to use the internet yet. Also mention that you think all the data usage is the iPhone itself connecting to update itself (update time and what not). You can say that these charges were never explained to you. If all fails, go to the store. You being there in person is going to be harder than the line "dropping" if you were to call.
Good luck!