Cancellation of contract

Hi am malebogo kedirileng I took I laptop on contract on 2018-01-23 and contract term date is 2020-01-13 I called vodacom on January 2020 to cancel the contract they refused to cancel it they say the contract of laptop is 36 months not 24 months and the contract that I signed is talking about 24 months not 36 months, I went to the shop on the 05 match 2020 where I took the laptop to talk to the manager she is telling me that the time I take the laptop she was not working there and what she know is that the laptop contract is 36 months not 24 months,I called vodacom after that to ask for help on 05 match they said they will escalate it when I get the respond from them they did resolve the matter using the number of the contract that I dont have a problem of,they did not use number of the contract that am having a problem of,so when I call them again I dont get solution,please assist me.

Thanks