How do I deal with being a backup friend?

I'm in high school, and i have a few friends. Like we all are like this group, and uhh I'm constantly being forgotten and ignored. They only reach out when they want something from me and when i want something from them, they just ignore my calls and msgs. They don't talk to me unless I talk to them. They constantly joke abt how I'm a temu replacement of one of their older friend and how unimportant i am. And everyone has their own group of friends and it seems like i can't fit in anywhere. When i tried talking to them about this, they just outright said that I was overreacting and crashing out for no reason.