Unable to download app from the AppSore

A few months ago I have downloaded an app from the AppStore for learninng English - Bright.

I have used it within trial period and as far it was finished I didn'd use the app. For the time being I can't download any new app from the AppStore as every time I am trying to it informes me that it is impossible to download new app because previous payment wasn't complete. I was trying to cancel the subscription but it is already canceled. I suppose the reson is that I dint have appropriate amount of money on my account to accomplish automatic payment at all.

I was trying to contact to developer of the app but he didn't offer any kind of solutions at all, even taking into consideration that according to the reviews on this app the similar issues are really common among users.

So, I was just wondering, maybe you can help me with this problem. I am brand new user of iOS and absolutely have no idea what to do next.

Thank you!