I can't delete some things from my iPhone Calendar that are not seen on my MacBook

I sometimes input a calendar event and then the even changes. I list everything under work because it allows me to set up alerts. If I go to my MacBook, I can delete them but they STILL show up on my iPhone, even months later, in the same slot. So then I have to put in another calendar event to ignore the first one, but it would be nice if I could just delete it. There is no delete option. Very frustrating. I can't change it from work. The only thing that clicks open is the alert ( and I can change to none) And I can see that I sent myself the invitation but when I click that, it is just a jumble of letters in upper and lower case after a /, which allows me to email or text or $pay that entity. Ugh! Very frustrating. I even got a new phone (not because of this) and it will. not. go. away.