I don't see calling someone over and over as harassing or seeking revenge.
I had an ex that for financial reasons, I couldn't get rid of her...she integrated herself QUICKLY into my life and figured out how to latch on in a way that would have made things very difficult for the both of us. And she'd do stupid things like wreck my car and not tell me until I got pulled over for only having one headlight (it was impossible to see the front of the car in the garage)...or decide that the place I kept my wallet and keys for 10 years was annoying her so she'd move them...before going to work and not tell me where, meaning I couldn't leave the house.
Quite a few other things like this...where I'm not going to say she was the crazy girlfriend (I have an ex that beats all this)...in most things she was rational...however when she fucked up even something minor, she ran away and hid from it. So there would be 30 or 40 calls trying to get her to answer so I could sort something out and she wouldn't answer. Which meant that I'd have to call her work. And her friends. And any possibility I knew how. Most of the things I needed to get ahold of her were things that were a block in my life until she explained what she had done to do something, and I just needed to know how so I could undo it. She wanted to wait to talk until I was 'calm and rational' of which if she would have just addressed it immediately I would have said "Oh? Ok...I'll take care of that for you".
In the end, I couldn't stand it any more and told her if she did something like this one more time, she was out. She took my car one day...didn't leave me her keys...40 calls later and I decided it was over no matter how difficult it was going to be for us. And ironically enough...the financial problems were far easier to handle than dealing with her any longer.
The problem with this is that the phone calls ARE open communication...the other person is trying to avoid the conversation. After a while even a sane person goes fucking nutso trying to deal with a fucking child that is afraid that mommy and daddy are going to yell at them so they don't answer the fucking phone or come home at 11PM hoping you are asleep in bed or any number of different ways they do to avoid honest communication, when a single message would have solved EVERYTHING in 2 minutes and no one would be angry.
Every single crazy girlfriend that my friends have that does something like this is almost always the responsible one in the relationship and trying to keep the relationship working knowing that it isn't and the other person is a dumbfuck that deserves to be thrown out in the street and never let back into their life. If your girlfriend does this, man the fuck up and leave...you will be doing her a HUGE favor because most likely you are the problem.