Mtn are data and airtime *******

I want to warn potential customers against mtn. I have a contract with it and receives 10gigabytes yet in a week's time its finished when im never even using my phone, i buy another 3gigs in two days all gone its been 5 months now and when i log a complain nothing happens they keep saying they r investigating meanwhile they are just sitting on their big asses in their big offices chowing our monies its about time we take our business elsewhere