Billing rose by approximately 50% for no valid reason

I have a top up contract with Vodacom whereby I paid R397 monthly(including insurance). Mid July I was offered a WiFi router contract for R199 pm which I accepted. 2nd of August R129.09 was deducted for the new contract plus the R397 for the existing contract. All of a sudden on the 1st of September R1200.07 was deducted from my bank account which no one at vodacom can explai.I called accounts and sales department but no one can give me an explanation for this big hike. Vodacom needs to explain this cause I'm not happy at all.