MTN CAllertunez autosubscription without my approval

It has now happened twice that I being subscribed to Callertunez WITHOUT ME COPYING the tune. As strange as this may sound, it also happened to a colleague of mine last week. I called 135 twice last week to unsubscribe.

The very same thing happened again yesterday - I am getting subscribed without me doing ANYTHING. I called an agent now and she said I must dial 155# - this number doesn't work - "Error performing request". How does an MTN agent provide the wrong number?

How do I PERMANENTLY block such callertunez in future? Please assist asap as this is a moneymaking **** - given that I have not copied any tunes,