I checked your account and I do see that you're upgraded to a 60-day trial of Pandora Premium. You should have received an email confirmation with details. Be sure to check any junk or spam folders that could have filtered it.
Your trial will remain active until 10/6/2020 and which time, unless canceled, will automatically convert into a real subscription.
To view your subscription or to cancel, you'll need to log into your Pandora from a computer. Click here and select the Subscription tab.
Let me know if you have any questions about Premium.