Billing headaches/Taking my money!

On the 1st of April I received my R350 airtime from Vodacom as always. With this airtime I buy 3GB of data every month for my phone. So on this day I by accident select a month-to-month and not once off data bundle and receives the following sms from Vodacom \ Your 6 month promotional Deezer 3GB MI Service has been activated". Frantically I phone Vodacom and asks the operator what this means. He tells me I do not have to worry as nothing may be added to my contract account without my signature. I once again ask him if he is sure"