MTN OVERCHARGING IT'S CUSTOMERS!

I just bought R10 airtime to make an urgent call but right after i loaded the airtime the MTN sms's came through as usual when 1 loads airtime state that your account has been loaded with x amount of airtime...than when i checked my balance only R0.50 was LEFT before i could even do anything. I called the customer service line and they couldn't help because nothing was showing on their system and the lady i was talking to started to speculate how my airtime disappeared and said that she cant assist any further. I've had this problem several times and I've never really got assistance from them instead i would just loose out on the airtime that i bought with my money. MTN used to be the best service provider but now it has turned to be the worst because its becoming more expensive by the day and inconsiderate to their customers