How to cancel a recurring payment that's pending?

I signed up for Match. I tried multiple times to cancel the subscription through the app and couldn't. I just received an email from iTunes saying they're billing me for a renewal. The transaction hasn't gone through yet. I found directions online to stop future renewals in iTunes & have fixed that. But now I need to stop this payment. I've tried to report a problem with the payment, but it's still pending, so it won't let me do anything to it. How do I fix this?