S6 will only make calls to numbers in contacts

[Android Central Question]

My girlfriend just went back to Australia. She uses a factory unlocked S6 (bought directly From Samsung).

She was using the phone on T-Mobile in the states, and now on Telstra in Australia. If she calls numbers saved in her contacts it goes through fine. However, if she tries to dial on locally, it says no network available. The girl at the Telstra store told her she needs a new phone. Clearly the individual simply doesn't know how to troubleshoot the problem. I've told her to reset the network settings which did not work. The internet, and incoming calls all function properly. Same with outbound saved numbers.

I'm trying to think of any other setting which could be throwing things off?

Thank you in advance.

 

[Tim1954]

Telstra tech support are good, you can do live chat or call them (on a different phone is good) and they can go through all the settings with her...
Let me one if she's OK to do this, I can shoot you the numbers she needs to call if she can't track them down...

 

[abrown3mtg]

I'm getting updates that make no sense. She called Samsung Australia and they said that because she has been in the USA for two years, the phone is now locked to the United States. This makes zero sense to me. It was a Samsung phone not from any carrier used on T-Mobile prepaid. Now she is being too dumb to call the USA to try and get it unlocked again.

Does this seem realistic? I really think she is getting people that have no clue what the hell they are talking about. Considering one employee told her the phone operates in the wrong bands (incorrect a sense well... considering she can get calls and internet functions). I really wish I was there to troubleshoot it.

She also can call Australian mobile phones apparently, but not landlines....