Telesales getting out of control

I am helping my parents with their financials and found their cell phone account extremely high with 4 cell phone contracts - 2 we are aware off but then there are 2 that was never even used. I contacted Vodacom via email to request them to proof that these were valid contracts by providing us with the voice recordings where my father agreed to these contracts. The reason for this is my father had a stroke and both contracts were loaded when he was in and out of hospital for medical treatments and he was in no mental state to enter into any form of contract. The only response I get from them: We are sorry to hear about your circumstances but you need to go to the police to get an affidavit if you think its *****. I find this unacceptable because this is not our problem they need to proof that these are valid contracts not us. I want them to answer me: Why would elderly people need more than 1 contract? My father was called again 2 weeks ago and I believe a 6 contract was loaded. I believe Vodacom need to investigate their tele sales centers because they are pushing sales working ********* pushing customers into contracts - disguised as upgrades - just to get sales.