I have it! Bubble is an app where you can talk to your idols. Not directly, but it's kind of like a group chat with all of the people talking to your idol with you, but everyone except the idol is blocked so you can only see their messages. Whether or not it's expensive is who your idol is. Depending on the Bubble app you want and which idol you talk to, the price may vary. For groups like ITZY, there are group passes that cost about $9 a month. Stray Kids is one of the groups where you can talk to individual idols, each ticket is about $3-4 dollars a month. If you have any other questions, let me know ^-^