Mtn customer service

I am an existing MTN customer, I currently signed up for two lines.<br> The other line is used by my son, I realised that he has been purchasing data bundles through self service without my knowledge.<br> I called MTN the beginning of this month and found out that I owe 3500 for the purchased data, I requested for reversal of the data and they told me is not possible . I asked if I can perhaps transfer the data and I was told is not possible as well. i asked the consultant to check if the purchased data is not recurring and she confirmed that it is not, she even further asked me to dial the USSD code on my phone to check. I did that and she confirmed that it is not recurring.<br> I then asked her to help me to arrange for the payment, she did that and also sent me an sms. she told me the first month which is end - April I will pay 500 and then the other 3 months I will pay 900. I agreed to that arrangement. To my surprise today I received sms confirming the purchasing of data bundles again, I then called MTN again to check, I was told that recurring data bundle was never removed the call is logged for the recurring to be removed.I have been misled by MTN en now another invoice coming my way.