iPhone 6 not working after unlocking

Hello,

My friend bought an iPhone 6 with T Mobile with plan and he is currently traveling out of the country. He had it unlocked before leaving and t mobile says the unlocking was successful. But he is not being able to make or receive any call on the phone now using his local sim card. The network bar says its registered but when he tries to make calls it asks him to put money on the account since its a prepaid account. But even after recharging the account he neither can receive calls or make any from the phone. What will be his best options here?

 

Thanks! I'll ask him to reset the phone, and also re-enter the saved WiFi passwords. But the international provider is compatible, I know someone else who's using a same T-Mobile iPhone with the same provider.