I'm unable to deactivate Vodacom Data Refill due to poor service.

Everytime I recharge they deduct R3 for data Refill . I've been trying to opt out on Vodacom Data Refill : I've used the USSD but it keeps on saying that there is an error and I have also tried to call their customer service but I cannot reach out to them due high volumes of calls they are receiving . This is bad because sometimes I want to use my airtime