Are you using the phone app for chat? If so try accessing on a computer instead. You have to be ready the second you are up. I know it says on the countdown to check every 10 minutes, or it used to, once you hit the countdown you need to watch it closely so when your turn comes up you are there to chat. If you are a minute or two late and they don't get a response they will close the chat.
You should get s response on Facebook messenger. The last couple times I had questions about the new plans they responded in a somewhat timely fashion. I have used Twitter twice but the last one after 10 days without a response I don't recommend it to anyone.