Have you changed/updated your OS of your PCs? Win 10 can consume loads with its updates.
Have you managed to make any progress with this yet? I am still going round in the same ridiculous circles with BT about my mum's high spike in usage over several months.
It has mysteriously reset to normal levels since I complained but BT maintain that they have done nothing at their end to change anything, and insist that their data monitor cannot be wrong. Based on my most recent contact with them, they seem unable to grasp that there is a potential issue about misrecording of data useage that requires investigation because it impacts other users as well as my mum. They will only deal with each case in isolation and although they have offered a deal on unlimited BB and to refund charges incurred, I still want to know what has gone wrong, and have asked that they review the way this has been handled.
They cannot offer any explanation for the high BB usage other than unauthorised access (and theft of the wifi password) which simply is not a viable explanation for many reasons. BT waver between accepting that the BB useage is very strange and agreeing it is highly unlikely that my mum used the data, to insisting she has used it because their reports say so. Its like a rather farcical good cop / bad cop scenario. Last night it was the bad cop that aggressively denied any issue and treated me with a level of disrespect I found astonishing. He did back off when he realised that he had completely overlooked the issue about the mismanagement of this complaint, and so had not appreciated that he was not offering any new information. He went on to blame his collegues for not clearly documenting what they had agreed to follow up and/or for making undeliverable promises.
The complaint has been passed around 3 different managers since it was escalted, none of whom had looked at the case in detail and so were unable to resolve anything when they finally get around to phoning (rarely on time, even if I phone to seek a response). I find myself constantly repeating everything to a new person who then does not do what they agree to do and so we start again. I have requested that someone take sole ownership of the complaint so that I can make some progress but it seems BT cannot operate that way.
Currently waiting for manager number 4 to phone me back so we can repeat the charade yet again.