Refusing my refund

I upgraded my contract at mtn in april and was called by a lady from mondo that processed the upgrade online.There were extra minutes and data added that I did not agree to or requested for it to be added.I call mtn to request a refund and for it to be removed or cancelled,thus far they cancelled the extra data and minutes but play the blame game as to who should refund me.The mondo consultant dropped the call in my ear and mtn says they have to escalate the issue because I did the upgrade instore when I explained to hundreds of consultants that it was not the case.The experience frustrates me seeing that I paid this extra amount that I did not budget for on time and no one can assist me.