Cell C charging me R171 for 5 seconds wifi use!

I ordered a wifi device from Cell in August and had it delivered at work on the 31st of August. I then activated it just before 8pm of the same day. Now Cell C tell me that I must R473 rand at the end of September! This is ridiculous because the contract says I am to be charged R189 per month. But when you look at the bill Cell C sent me, they charged me R171 for 5 seconds of internet usage! There is also another charge of R66. I do not know why they did not pro rata the data for the 31st August. Now they claim that I used the data, finished it and began using airtime for wifi rather than data! I am so angry. This is a useless network and I am going onto my social media to tell everyone who will listen that they must never use Cell C data or buy their Wifi services. I am demanding that these additional charges be cancelled from my record. <br>