How to delete Subscribe calendar?

Hello fishingsiao,

Thank you for using Apple Support Communities. I understand you're unable to delete a calendar subscription on your iPhone. I can help point you in the right direction.

The option to delete a subscription would appear, if you added the calendar subscription to iCloud. That information is outlined here: Use iCloud calendar subscriptions With that being said, I recommend going to Settings > Password & Accounts. Under the section of, "Accounts" look for the calendar subscription you'd like to remove and select it. Then, scroll down to see if you can delete it, or turn off the calendar if you don't want to completely remove the account.

Kind regards.

See this,

If you go to Calendars at the bottom of the screen there, do you see a calendar listed that matches the color of these events? If you see a strange calendar there under Other or Subscribed, can you uncheck it? Then you may want to check, it seems they get will add a strange mail account. Go to Settings>Passwords & Accounts and see if you find a strange email account there. It may be where the calendar syncing is coming from. Delete the account from there. You will also want to check Settings>General>Profiles, and see if there is anything unusual listed there.