We had the same problem but mine already being solved with helps from many parties including our friends fron celcom community. Thanks @spartan & @nuar_95 for your kind help last time 😄
So here are some suggestions of steps to be taken :
1. Do manually from subscription page. In your existing account, just click on “Menu”, go to "My Account" page and click on "Cancel My Subscription".
2. If it's still unsuccessful, directly contact iflix support team by emailing them at iflix@support. From my experience, they want you to provide them with your support ID & phone number before they can proceed with the unsubscription process. Within a week, I managed to successfully unsubscribe iflix apps from my phone. Now I dont have to pay hidden charges anymore. I hope you'll get the problem solved soon. Good luck !