Vodacom's trash service!!

I called vodacom on the 27th march to cancel the data contract I had with them. I was sold a new contract with 20Gig data for R139. I took up the offer, which was supposed to kick in from April. I waited for the WiFi router, which was eventually delivered in May. I received my April statement but the payment due was far more than the R139. I paid it anyway. I've now received my May statement with a ridiculous R4000 due by myself. I called Vodacom to query this, since Monday 11th June. I have been speaking to different consultants and been given reference numbers but no resolution to my query. VODACOM IS TRASH! Iwill not advise anyone to sign up with them!!! The team leader, Christina Dyosini was supposed to call me but I'm still waiting for her call. Vodacom's service is pathetic, to say the least. I've been their client for more than 15 years