unhappy client

I am a Telkom client & have their contract where I am supposed to get 1gig a month, for the past months they have been faithful & delivering but now in May I don't know what went wrong, my data suddenly got finished on the 12th day of the month. When I called the call center they say I have used it all up, whilst I don't even download anything or use that much of internet & I've been using it on the same things on the past month, I really don't get what made it so different this month, cause I just use it on social networks only. The guy who was assisting me on the phone said he will email me the breakdown of of my usage for the 12 days but he never sent it, I'm so disappointed with telkom , I wish I could just change networks cause this is really not fair, as I am a faithful client who every month without fail.