Continued contract without permission

Two years back I signed a 24 month 10gig data contract with Vodacom through CelluCity in Port Elizabeth for R299 per month. After the 24month contract Vodacom just continued with my contract and increase my payment to R503 per month. Never realize it as I was not using it the data anymore because i installed uncapped internet. After I discovered it, I immediately informed CelluCity and they told me Vodacom is the only one that can resolve my issue and reimburse me. They phone vodacom head office in PE and the manager in charge told them they reimburse if i didn't use the data. I showed the lady at CelluCity the proof that i didn't use the data. I also phone vodacom customer to check and they confirmed that it doesn't look like I used it. Vodacom told me that the contract went to a month to month basis after the 24 month contract. According to my contract it only state 24 months and nowhere on my contract does it state it will go to month to month after that. There is also no evidence from Vodacom that they informed me that the contract will end soon or that it will now roll over to month to month. Can you please look into this matter as i or the contract i signed didn't give Vodacom the right to continue with my contract Kind Regards Preston ********** 515