Vodacom cheating us out of data and other things

On Saturday 16 June I purchased 1GB of data at R149. On Sunday I get a message saying I have 198 MB left. I have NEVER gone through a gig of data overnight! This is something that seems to be recurring recently as well as it happened a couple of weeks ago.

Also I closed my contract with Vodacom in January and I was told to pay spme R400 odd rands. I did. Last week I received a letter of final demand stating that I owed R261 on the contract. I paid it and sent pop to Vodacom. I have not heard from them in this regard. I also don;t understand why I am still getting billed on a closed contract!