Pro Chat Support + Inviting Team Members

I thought Pro came with priority support and chat, according to the description. However, I don't see that anywhere. In fact when I emailed support it said we will get back within 2 business days. That's a long time when you're trying to get projects off the ground. 

My other question is what is the difference between "inviting team members" and "assign seats"? I want another team member to have full access to what I have, can I do that with pro?

Thanks