Internet so fast that Data disappears without me using it.

So I keep an eye on my dad's internet usage at home, recently (since September 2017) Somehow from using an average of 40GB of data per month, My dad has been using all his allocated data(200GB). So a cheeky sales person in store convinced him to upgrade his contract that was near completion to an uncapped line.(If I were with him I would have told him not to) So now My dad has payed for an upgrade which has not even been put through processing 100% yet It's not your R399 uncapped bundle, my dad is paying for a 40Mb/s line uncapped. On a good day which is normally 4 out of 30 days of the month, the download speed on the line can get up to 27Mb/s but the rest of the time the line speed averages between 1Mb/s and 3Mb/s. I am disgusted with telkom when it comes to ADSL/VDSL service the people tasked to help a person don't know what they are doing most of the time and when you need help it somehow always takes more than 3 weeks. I am completing my MCSD at the moment, I have made it impossible for a hacker to get the passwords, I have gone to the extent of switching off the wifi, and only having my Dad's PC connected via LAN Cable. I have set up monitoring on the data usage, if the data carries on disappearing, well it's not a hacker, its not the household usage, I wonder could it be ? My word, the only other entity envolved is telkom could they be the people *****ING ? This better be fixed I'm taking it further.