Renewal and canceling a plan

Hello I purchased an HO sim in May. And I purchased credit for one month from a store using cash. For the next month I used the app and added credit (I did NOT activate the automatic monthly plan). Now I’m leaving Europe and want to stop the plan. Will it automatically stop when I run out of credit in the app or will I be charged monthly on my credit card ? As well if I come back to Europe next year can I re-activate the plan using the app or does the sim deactivate after 6 months of no usage ?