Line Messenger (new phone number after migrating)

I have been trying to find a solution to a problem my wife had when she moved to Australia last year. She was unable to retrieve her Line account after changing her phone number. I have gone through the Line help center information, and it seems that everything I get is an answer regarding new devices with new phone numbers as opposed to the same device with a new phone number.

So far, I have tried linking the account to Facebook, which has worked, but the phone number is still there in my profile, and I cannot tell whether of not my Line account is now based on my Facebook account or whether it is only linked for importing contacts.

I have also tried transferring the account to a new device, using my iPad and logging in using Facebook. That seems to work well enough as it logged me out of my iPhone app, seemingly making my iPad “home base” for my Line account.

It seems like both of the above, done in the same order, will enable me to take out my SIM in Australia, add a new SIM and log in with Facebook, but I have found some places on the internet where people have said that it sends a verification code. Does anyone know where the verification code is sent? Is it sent to the phone number that was originally used to set up the account? Or will it send it to the iPad that is now “home base” for my Line account?

This seems to be a potentially tricky process because it is not clear where the verification code is sent. Can anyone who has been in this situation tell me what to expect?