Hi, I'd like to help you with your question.
It sounds like this friend is telling you that they are not interested in being friends, at least not the normal kind. To be nice to you one minute then cut you out of their life the next or to tell you they want to see you then go on vacation and not let you know are not a signs of a true friendship.
It sounds like that this person either has mental health issues, primarily a personality disorder, or they have anger issues and are taking it out on you. Although having an idea of what might be wrong is good, it still doesn't help you.
This relationship, based on the length of time you have gone through these games and the attempts you have made to repair the relationship, needs to be over. Regardless of the reasons for the behavior, this person is not going to act normally in your relationship and the time and effort you are putting in maintaining your end of the friendship is not working.
Since you have tried a few times already to contact this person and they have not responded, you should probably just let it go. If they contact you again, just say you have moved on and no longer desire contact with them. If they persist, then hang up or move away from the situation. Keep responding in the same way until they leave you alone.
Here are a few books that you can use to help you understand your relationship better and how to avoid another one in the future:
When Friendship Hurts: How to Deal with Friends Who Betray, Abandon, or Wound You by Jan Yager
Toxic Friends/True Friends: How Your Friends Can Make or Break Your Health, Happiness, Family, and Career by Florence Isaacs
You can find these on Amazon.com or your local library may have them for you.
I hope this has helped you,