in August 2017 we bought a smartphone LG G5 through Amazon Germany. The phone came from the German company blufone.de; it was new in the original sealed case (original bill is available). The phone came with T-mobile branding (i.e. you get the T-mobile logo when you switch it on and the T-mobile jingle), but without any SIM lock or network lock. Until a couple of days ago we used it with our German SIM card without any problem.
A few days ago then we updated the Android OS from 7.0 to 8.0, using LG's tool 'LG bridge', downloading the new version via USB cable (as no update was available over the air). The phone works perfectly well with the new Android version as far as the different apps etc. are concerned and anything that only requires wifi, but now suddenly the SIM card no longer works and there is a network lock! As the phone was bought NEW in the original sealed case this is extremely annoying, We are now trying to find out how to remove the network lock, which really shouldn't be there (after all we paid more than 300 EUR for the phone which right now cannot be used at all to make or receive any phone calls!). Does anybody have any idea what can be done?
Obviously we are not customers of T-mobile, as we are based in Germany. Apparently the unlock code can only be requested if you are a T-mobile customer - or is there any way for us to get the code in our situation? I cannot even set up a T-mobile account to communicate with customer service as we don't have an American telephone number and the registration tool doesn't accept foreign phone numbers.
One more piece of information: looking at the list of apps under 'settings', there is an app 'Device Unlock' (indicated as 'installed'). So I suppose there should be a way to enter the unlock code if we can get it (although I wouldn't know how to do it as you cannot actually 'open' the app).
Thanks a lot in advance to anyone who could help us get our phone back into a properly functioning state!