Hey there iphone_user_rch1,
Thanks for reaching out to the Apple Support Communities. So we understand the issue correctly, are you only having this issue with calendars synced from your Google account, or does this issue occur with calendars synced from iCloud as well?
If this is only occurring with your calendar synced with your Google account, have you gone through the steps here to turn off notifications for those calendars: Modify Google Calendar notifications - iPhone & iPad
Turn off notifications
To turn off all notifications for Google Calendar, you can change your calendar’s default settings. Because notifications sync between your mobile device and your computer, you can change your settings from either the app or a computer.
1. Open the Google Calendar app .
2. In the top left, tap Menu .
3. At the bottom, tap Settings .
4. Select a calendar.
5. Tap a notification and choose None. Repeat for each notification.
If you have multiple accounts or calendars, repeat these steps.
If still having issues after going through the steps above, you may need to reach out to Google's support who may be able to provide some additional information or troubleshooting steps. Check out this link for help with reaching out: Google Calendar Help
Take care!
