MTN taking airtime after topping up

MTN took my airtime after i top up 2 times. I have been using this number for close to two years. I call the customer care and they told me i have some subscription which i don't know of because i never subscribed to anything. I was told customers ignore messages and hence they end up with subscriptions, how is that possible? Their solution is to cancel the subscriptions which i never made in the first place instead on reimbursing my airtime because i never subscribed to anything. They said they are logging a complaint and will come back to me in 3 days on the 18th of August 2020 but they haven't done so. My question is how do i get subscriptions i never subscribed to and what guarantee do i have that they won't come back since i never subscribed to them before?