Why do I need data to text in a group chat that has Samsung users?

I’m an iphone user and am currently in a texting group chat that consists of Iphone users and one Samsung user. Anytime I want to text or receive messages in the chat, I have to have data on, and having wifi on does not work. The other iphones in the chat are able to text on it while connected to wifi? Is there anything I can do to fix this?