Vodacom bill twice in one month

I decided to upgrade my cellphone contract and Vodacom decided to charge me twice in one month for my plan. I contacted them telephonically where the agent tried to convince me that the costs are legitimate. Because it takes long time for the call centre to answer the calls I cannot wait in line and thought it best to ask the call centre agent for a relevant email address. I sent two emails and no one answers the email. No surprises there. Be ware.