Hi,
This forum isn't the correct place to look for 1-on-1 support, unfortunately, although
I'm happy to provide some advice for you:
You should either
contact billing for a question like this,
check the help center/docs, or attempt to follow your intuition: if it complains that billing isn't enabled, and you're not sure if you've enabled billing, you should keep trying to find ways to enable billing. When you say "seems it doesn't help", that doesn't provide enough information for anybody to help you. What happens when you attempt to add a billing account? Did you go through the steps to upgrade? If you didn't do these things, you won't have any free trial credits, since that requires
Best wishes,
Nick