Vodacom struggling to rectify my Handset amount

On the 17th of April I sent a request to Vodacom in order to cancel my handset but keep my Data. It was 2 months from my "end of contract" date and I wanted to see if I can cancel early. Only to receive information that my cancellation amount is more than R4000, which was impossible, because my monthly bill was around R900 per month. I have been struggling since then to get Vodacom to sort out my handset amount and I have received a June Bill for R4900. I keep on phoning and sending E-mails. I did receive an E-mail with an acknowledgement that it is a Vodacom error, but I have been waiting for almost 2 months now and end of June is drawing closer and closer.