Vodacom savage where upgraded my contract without my consent

Vodacom upgraded my contract without my consent for further 3 years and I am very angry. I told them to change my number to prepaid as I'm not using it and I'm unemployed. That's very selfish to upgrade. I have been a loyal customer for many years and to be treated like this is savage & bad from Vodacom.

Please change my number to prepaid asap.