Not honouring undertaking ref***

Cell c are disgusting. They have not kept their undertaking to debit the correct amount that they gave me in black and white by Mr. Patrick Mphuti. He assured me that on 30.04.2015 the debit would be R153.99. Cell c debited R189. which i instructed my bank to return. I have since been receiving threatening sms s that i would be cut off and that i would be debited R70.00 for returning the debit. I wrote a complaint on Hello Peter on the 3rd of may 2015 in which cell c answered that Mr P. Mphuti would also contact me but this never happened. I wrote 2 emails to mr. Mphuti but received NO reply..I logged another complaint with Cell c referance *** but still no joy. They say that when my complaint is resloved they will notify me. This NEVER happens. I said that cell c may debit me yhe correct amount of R153.99 and no other amount. I WILL NOT PAY the R70.00 bank return fee as its not my mistake. This is the last attempt to try and have problem sorted out failing which i am prepared to take Legal Action. I have all the proof available.