I want to cancel my Photoshop subscription. I no longer use it, but the system won't let me cancel because of a payment issue. Please help me cancel my plan and explain any outstanding charges.

You incorrectly posted this in Adobe Stock. This belongs in Account, Payment & Plan which handles account matters.

Fellow users here can’t help you cancel. You must resolve the payment card issue first, otherwise the online system can’t process your cancellation. 

https://helpx.adobe.com/account/individual/billing-and-payments/payment-methods/update-payment-information.html

Applicable refunds or early termination fees will be applied to the active payment card you provide on file.   

Log-in below: 

https://account.adobe.com/plan

Click Manage Plan for more options.

Or click the online chat icon and ask for an AGENT.

Hope that helps.