Airtime vanishing daily from my prepaid balance

Horrible experience.

I've reached out to the MTN customer support, with no answer.

I've gone in-store, and their customer service rep was of no use.

Situation: every day R3 vanishes from my prepaid airtime. I've checked via their automated menu, and I am not subscribed to any services that will take airtime. I've gone in-store, and confirmed the same. I am not subscribed to ANY services at all. I have more than enough data on my account, so it's not airtime being used in place of data. I rarely make calls, and I don't send text messages. I use data all the time, but I keep on top of how much I have, and I ensure that it never drops to zero.

I work in mobile app development. I would know if I subscribed to anything.

As a test I loaded R30 worth of airtime on 17-11-2017. Every day that decreased by exactly R3.00, and as of today I have a ZERO balance. Despite no calls, and no text messages.

Despite being assured that I am not subscribed to anything by an IN-STORE MTN service rep.

So what the hell? I want my airtime refunded, before I move to another provider.

MTN is being spectacularly useless here, and effectively *****ing money from me.