UPGRADED CONTRACT WITH OUT KNOWLEDGE OR CONSENT

I have received my Vodacom account today which informs me that I owe R 787.50 my normal monthly account is R 158.50. I contacted Vodacom (082 111) and was told that my contract has been upgraded on the 09 March 2015. I then explained that I did not nor have not upgraded the contract, I was then transferred to the UPGRADE Department who told me that I upgraded in March to which I responded I did not. I was then asked to hold while they contacted the Witbank Vodashop (which was closed) I was then asked to contact the Vodashop and to make out an affidavit to state that I did not upgrade my contract.<br> I am more than 100% that I did not upgrade my contract and I fail to understand as to why I must spend my time, effort and money to rectify a problem that VODACOM created themselves.