Out of airtime on the 1st of january

Vodacom has done this many times before, where they deplete my data without even informing me which is one...I bought 200mb of data this morning and R180 of airtime is finished? This doesn't make any sense because I use Wi-Fi...only when I needed to make an urgent call I realised my airtime is finished!.. I manage my data usage properly because of previous situations of Vodafone just depleting it. My account should be refunded immediately because this is enough.