Sophia here from Shopify. Welcome to the Shopify Community!
The best way to tell which stores are being paid for is to login and check Settings > Billing in the admin. When you're logged in as the account owner, you can also follow these steps to close a store.
If the second account was on a trial period but no plan was selected and no billing information was added, the store would freeze at the end of the trial and essentially be considered closed. If you're not sure whether you would have selected a plan on one or both stores, it's definitely worth checking to see if you can login to both. Please let me know if you have any trouble with that.
We do offer live chat support, which you can access through the Shopify Help Center. Due to high call volumes, live phone support has been shifted to a callback system so that you don't have to wait on hold. This option will be listed so long as you're logged in and current callback volume permits. Otherwise, we're happy to help you here on the forums any time, as well as via email.