Data Consumption

I have a Wi-Fi Router contracted by Telkom Mobile. I have it since May 2016. It's loaded monthly with 2Gig of Data and i also have 5Gig that is also on contract from Telkom. I have never had any issues with them until Saturday the 26th August. I normally use first 5Gig until finished then insert the 2Gig sim card on the router. The 5Gig ran out of data on Friday afternoon 25 August then i only started using the 2Gig on Saturday 26 August around 10am only to wake up past 5am on Sunday 27 August the data was finished. This surprised me since i only use the Wi-Fi router for the Internet on my phone and i only used it on WhatsApp and Facebook but i never bothered to contact Telkom. Then yesterday the 29 August i purchased 1Gig around 1pm and again this morning 30 August around 10am my Data was finished. I then contacted Telkom Mobile to be only told that there's nothing they can do as their system is working normal. I don't have any applications running on the background, i disabled them since i purchased the phone in 2015 December.