Vodacom is very bad

I had a cellphone contract with Vodacom, which expired in March 2018, I then received a bill of R420 in May 2018, I called Vodacom to inquire about the bill since my contract has expired. the consultant told me the contract renewed itself , because I didn't call to cancel it. I am no longer using Vodacom's services, yet I am receiving the bills every month. I try to call them again , I spoke to the consultant by the name Dudu, she couldn't assist me, then I was transferred to another consultant who said I should pay R1140, in order for the contract to be cancelled. why should I pay for the contract that renew itself? why should I pay for the services I never received? till date no one has ever called me from Vodacom