unsubscribe me from the service

You can do that here from that page that the Manage Subscription button takes you to - https://railway.app/account/billing

refund the renewed subscription

You can request a refund on your applicable invoice on the same page previously linked, if you do not see a refund button that invoice would not be eligible for a refund.

Your service is too cumbersome to relate with.

I would very much appreciate if you could elaborate on this.