Vodacom Smart M misleading

I specifically asked the agent who attended to me if it will be possible to buy additional minutes if I do run out while I'm on the smart M package. After contacting Vodacom today, the agent informed me that I am allowed to only add Data and Sms's not minutes. The only way to add minutes to my contract is to migrate to a bigger package. This is unacceptable and very misleading . I was made to believe that the Vodacom packages are very adaptable. What now?