To ensure your Deutschlandticket subscription ends by the close of the current month, it's advisable to cancel it before the 10th of each month. 

Simply go to your home screen in the NAVIT App, click on 'See more' on your Deutschlandticket card, and scroll down to the ‘Danger zone’. There, you'll find the option to "cancel subscription." Follow the prompts to complete the cancellation process.