If you do not cancel before more than 24 hours of the trial period ends, two weeks after the free trial ends, it will be automatically charged.
If that is not the release of the automatic update before more than 24 hours of period end date, contract period will be automatically updated.
Please have logged in to the iTunes of the iPhone · iPad terminal in the same AppleID the time of purchase (Settings => from the paid version in the app).
At the time of change model, you can restore previously purchased paid version free of charge.
Of automatic updating billing is done within 24 hours before the end of the contract period.