Why are subscription payments not ending when they are supposed to?

Infusionsoft is taking payments after a subscription period has ended. In general this is normally one extra payment. I have reported this three times and all I get told is “we’ll look into it and get back to you” but it’s still happening and causing us a lot of manual work. I am really getting p***** off with this and I am now seriously considering moving to an alternative crm as I think infusionsoft has had its day. Can anyone help resolve this because I am really unhappy with not only the ongoing additional work involved but also the fact that this issue has not been sorted.