Why is my phone not connecting to an American network when I'm in the States?!

[awalter]

I bought an international factory unlocked Samsung Galaxy S5 off of Amazon. I live in Canada and it works great here. However, I went across the border to the United States yesterday and it wouldn't stayed connected to their network. I managed to get onto AT&T for one minute and was able to send one text but then it was gone. My friend had full signal though. I turned off my data before I crossed but in the past with my old S2, it would just automatically connect to AT&T. I had signal but it was the emergency only one. I searched for networks and found two but it wouldn't connect. I did find the setting to turn my mobile data on. What's going on?!? I need my phone when I go to the States!

 

[dpham00]

What carrier are you using? Are you switching sims when you go to the usa?

Sent from my Verizon Samsung Galaxy Note 4

 

[AZgl1500]

does your carrier have a reciprocal agreement with a carrier in the USA?

I've only been in Canada once, and my Verizon phone worked to call back to the states while I was in Canada.

 

[IAmSixNine]

it might also help to double check the "international" version you bought and see what actual frequency bands and protocols are in it.
Not all phones are made equally, and most international devices dont always work int he USA because we dont use some or any of the international frequencies. Heck it may even have the wrong protocol on the right frequency. Lots going on under the hood of our phones now a days.
If it were me i would check there first.

 

[awalter]

I am using Virgin Mobile in Canada (which uses Bell towers). I have never switched my sim card in the past. It has always just connected to AT&T. How do I tell the frequency bands? I think it uses GSM?!? I emailed the place I got it from and they said it definitely should work in the States and is probably a setting issue. Before I crossed over the border, I went to Settings and then Data usage and unchecked Mobile Data as I don't want to get charged for Data roaming. When I was in the states, I went to Settings, More Networks, Mobile Networks but did not have Mobile Data checked off. So I checked it off and kept the Data Roaming unchecked. My network mode is set to auto connect to LTE/WCDMA/GSM. When I searched network operators, T-Mobile and AT&T came up. I clicked on them and it asked if I wanted to register with them and I said yes. But then I got an error saying it wouldn't connect. I also got an error saying that since I turned off my data while I was in my service provider, I couldn't turn it on in the States. Unfortunately, I do not live near the border and can't test things out until I go to the States next which is on February 16th. Any suggestions?