Telkom LTE deal - Data dissapeared

I recently signed up for the Telkom 20gig day and 20gig night package. We received our router ect in order. I setup the router and all seemed to go 100% good speed ect. I changed the password to connect to the wifi as advised to something no one would know. I am aware that because we got the deal late in August we will not be billed/given the full 20/20gig but only +- 8/8gig. Last night after making use of the internet could not have been more than a gig data, when I opened my browser again it stated that the data has been used up. We have made use of the router but not that much that it already used up 8 gigs of the day data. I spoke to a lady from telkom but she cant help me she gave me times of when 3gigs ect but those times are all times we are not home. Then she said we need to take out the sim card and switch off the router when not in use, no one advised us of this and it is really unacceptable!! Now I must pay for 8 gigs that we did not use??! Her explanation is that as long as the router is on and the sim is in data will be used even if nothing is connected.. This is not stated anywhere and I have never heard of a router that works like that as what is it using data on if no pc/tablet/mobile is connected. Another guy from telkom told me it might be the same thing that happened with vodacom users where the data dissapeared but he couldnt assist me - different department. I want clarity on the situation and would appreciate a manager or higher authority to contact me asap!