Important: Make sure your current phone number is registered to LINE
If the phone number you registered to LINE isn't the same as the one you're currently contracted with, you may suddenly become unable to use LINE.
You register phone number A to LINE, but then cancel or change it.
You continue using LINE with the canceled phone number A still registered to it.
A certain amount of time passes, and someone else makes a new contract with phone number A.
The person newly contracted with phone number A registers it to LINE.
Phone number A is removed from your LINE account, which then becomes inaccessible.
Once a certain amount of time passes after canceling your phone number, it can be contracted to and used by someone else.