What do I do if a guest keeps spamming me?

Okay, so there is this guest who keeps spamming me on one of my stories asking me to do something in a story. I tried to compromise with this person, giving them a little bit of what they want, while still enjoying writing it, but this guy/girl won't leave me alone. They want me to change it in a way that I won't enjoy writing. I've tried telling them to stop, and they keep on reviewing under different names, thinking I'd be stupid enough to not know it is them. What should I do? I really like this story and I don't want to change it, because I really enjoying the plot line I'm writing.

Should I just stop writing this story? In can't really block them...