SERVICE IS REALLY DISAPPOINTING

I received a phone call from Vodacom saying that I am a valued customer sometime August 2015. They were offering me a good deal on 2gigs per month for my S4 Mini. I took it because it was a really good deal. After details were exchanged and I was assured that the debit order will go off on the 1st of every month, the first 3 debit orders were successful. November is when everything went wrong. The debit order bounced and I was charged R100 for it, and it kept bouncing every time they sent it to debit. I kept calling and making arrangements for a re-submit for a debit order but the debit order wouldn't come through. I finally called Vodacom on the 12th of Dec 2015 and requested that they cancel my debit order because I am being charged unnecessarily for this error that they keep doing. I was advised that it's cancelled. I made a transfer to clear the balance for that month. Yesterday I saw a debit order go off my account, why would you say that the debit order is cancelled and yet it's not cancelled. This is really disappointing because I really like Vodacom offers but this is going to cause me to cancel the whole package altogether. I prefer to make transfers myself. Please help??