A Newbie with old habits

I am on a 5GB day time and 10GB night surfer plan WiFi router. I have always used not more than 2GB a month when I was on prepaid. I use work WiFi during the day and this router at home after hours. But this month since the inception of my contact with Telkom. I have supposedly "used" all 5GB in a space of 7 days as my day time data was finished as of the 7 of October. In June it finished on the 1st of June(same day it gets reloaded on) 11am in the morning to be precise. I complained about this to Telkom at Cresta shopping centre. Where I was told that it was used and they had no further explanations. Instead they passed the buck telling me basic information such as switching off my auto-updates, which is something we all do nowadays, especially me coming from a prepaid lifestyle with data. Told me to create a pin for my router, which I told em I already have, coz someone could of used my data. When I asked for them to show me which devices had connected to my router, they told me they can't. I already had assured them that I am the only one who connects and has the password to this router. But they still persisted on the abovementioned excuses.

Furthermore this month, I asked for my billing usage to be sent to me and it was sent in a format that cannot be opened, I asked for a pdf format, which I am yet to receive. Asked to cancel my contract and yet to get assistance. They are really taking us for a joy ride and I am done with them. There must be an ombudsman for telecommunications companies.