What you are describing is a typical membership-based business and the way to calculate achieving the highest possible conversion rates. However, this doesn't necessarily mean having a high chargeback ratio. You should work on improving your customer care and support to reduce that chargeback ratio.Clients get called and sold an subscription. To get a higher closing rate, free trials are being used.
Most of the people forget to cancel subscription before the free trial ends.
Also a small % of the CB‘s comes from not having enough funds at the time of debiting.