Failure to cancell contract that has expired

Vodacom has, despite several emails to customer service and cancellations, refused to cancel my contract that has expired and run it's contract term. I have moved overseas more that a year ago and still paid the monthly fee.

I tried calling the call centre from overseas but got cut off, so I got in contact with the Vodashop where I opened the contract. they could not help me and suggested that I email ********** which I did. No cancellation and still keeps on billing me. I also e-mailed ********** but no action, not even a reply (except for the automatic reply stating we have received your email).

Why is it so difficult to interact with a company??