Incorrect billing

I have received the most horrible experience with vodacom even the call center agents aren't able to assist but provide me with possible answers which aren't accurate, but prediction which are false , I have top up my data 3 times today in less than a min I check my balance it state I got 1.00mb after 5mins I receive a massage stating I have 5.00 mb which doesn't add up , mind do I recharge with money which is being wasted , the sad part of this I only use whatsapp, I feel like I have been overcharged today and while the network is poor . How does 100mb with a poor network gets utilize within less then 5mins ? I have lodged a complaint with the customer care even now I haven't received any respond