How do i delete a calendar from my iphone

A friend recently needed to add his icloud subscription to my phone so that he could access a contact stored in his iclould while he was away from a computer or his phone. While doing so, he accidentally merged his calendar with mine.

I've deleted his iclould from my phone but his calendars (and reminders) are still showing up in the merged calendar (even when i uncheck the calendar in ical).

I see where i can delete each calendar but i keep getting a warning about it removing all the events. I'd like to remove them from my phone but i don't want to impact his iclould calendar.

Can anyone help? Is it possible to remove the calendars one at a time and not have them delete from his icloud? (Again, his icloud has been removed from my iphone)

thanks