VODACOM *****ING AITIME AND CHARGING FOR SERVICES NOT RENDERED

Vodacom *****ing airtime. i took a top-up contract with a R450 subscription. This means when my allocate airtime runs out, i have to top-up more airtime. Vodacom has been billing me for airtime i know nothing about . I was billed between R150-200 more for airtime which i have never received nor used. I never requested for advance but my bill says its for advance i requested..kanjani cos i always top it up when its finished