Book Part cannot be deleted

Hello all,
I need your help, please.
I’ve added a “Part” to the book and now I cannot delete it. If I delete that “Part” all the chapters under it will be deleted.
I’m not sure how to get rid of that “Part I” which keeps showing up whenever I export the files.
I tried my best to delete or remove it, but to no avail.
Can someone please help?
Thanks,
Michael