Where to get billing support?

It seems that TravisCI no longer allows users to create support case. So how can I get support regarding my billing?

The story is, I did have a subscription that due on the 16th every month. However, last month, there was an invoice at 8th December which state no SUBSCRIPTION PERIOD. I do have another plan for another organization which dues on the 17th, and it seems to works fine (still, December invoice has no SUBSCRIPTION PERIOD).