*****/Unauthorised billing

I took out a MTN contract in August 2013 and only found out today that i have a subscription to Victorious Technologies which i certainly did not subscribe to. I dont even know why they billing me and for how long this has been going on. I never received any sms/phone call nothing, but yet they deducting from my account.I blame my kids for using up my airtime each month never realising that this was happening. I am certainly not going to leave this matter like this. I demand a refund VERY VERY DISAPPOINTED!!!