I have a sad, depressing friend problem. Help?!?

So last year I met 4 wonderful friends(girls) . Throughout the school year we have been so tight. We were like sisters. Then one of them moves. Things started to change between the rest. The other three were acting mean to me. Making rude jokes and harassing me. I thought it was normal to joke around. But then they crossed the line with talking behind my back. I shoock it off. Then a nasty rumor spreaded. I told them it wasn't true! But they didn't believe me. Until one day they did. And things got better(: then it's summer. And we promised to hang out with eachother. Everytime I ask to hang they don't respond or make something up. Then I see pictures of them on Facebook together and it makes me so sad. Is this the end of my friendship with them);