If purchased through Google Play, you will need to cancel the subscription yourself.
Please refer to Google's help page for cancellation procedures.
▼ Google Help
How to cancel or change your subscription on Google Play
※ Please cancel at least 24 hours before the auto-renewal deadline.
Even if you cancel your subscription, you will not immediately become a "free member", and you will still be able to use the paid features of "with" for the period you purchased.
※ After the contract renewal date has passed, you may have to wait for 2 or 3 days until you become a "free member".