Group Text

Hi, for about a week now I am stuck in a group text that is sending inappropriate porn ect. I don’t know anyone in the text and based on the replies, many other people on the text don’t wish to be on it either. There isn’t a way to “leave the conversation” as with other group texts. I have gone through and tried to block each person and that doesn’t work. It seems to be a computer generated list where the sender changes their number each time. Any ideas? I get them all day/night, over 20 this morning.