Billing Issue of an unwanted payment

Hi, I had an unwanted Auto subscription of a VPN app named "Hotspot Shield", so i emailed the HotspoHotspot Shield Customer Support and they solved my problem and cancel the subscription but unfortunately there is still an outstanding bill in my purchase history, So when I asked them for this problem they answered me back "Turns out we don't have access to the iTunes' billing system, so I would recommend you contacting Apple support for further assistance."

So now I have problem on updating other apps in App Store because of this problem.

Please assist me in this problem

Regards,