Disappearing data without change in use

Vodacom mobile router contract customer here. It's a trap, when I took the contract it was r270-330, it's 18 months later and I'm already paying R455, I don't know how. It's 200gb, and finished on the 16th of May already. You can't get through to anyone coz always line busy and TOBI can't help. I have not changed use of data but Apr it finished 25th and now this!