I am still dealing with them - they have offered a 'solution' that will mask the problem but not fix it and have waived all the charges levied so far as 'a gesture of goodwill'. However, I have chosen to escalate this to the next level of complaint, and intend to follow through right to the Ombudsman if necessary, as I have suspicions that BT are using the unlimited broadband option to mask an ongoing problem that is causing huge distress for people like my mum (and your dad). These are not isolated cases - a quick Google search will bring up many such cases where BT customers have sudden inexplicable spikes in their data usage, so it seems to be an ongoing problem (beyond the 2014 FON fiasco which caused similar issues).
BT are adamant that the reports and checks that they have run are infallible - if their systems say my mum has used this data then that is the end of it. Interestingly, since I became involved her usage has miraculously reset itself to near normal levels - but BT are not letting on if this is due to something they have changed. I remain hopeful that they have done something quietly that has remedied the issue but I can no longer monitor the daily usage as in my mums case they upgraded her to unlimited broadband to 'fix' the problem. In doing so they have masked her usage figures on MyBT as they recently removed the facility for unlimited customers to see their braodband usage data.
Despite cancelling the unlimited upgrade within one hour of it being agreed, and despite two separate BT employees confirming that it was cancelled that day - lo and behold, her account was switched to unlimited anyway and has remained unlimited on MyBT ever since. The broadband usage figures disappeared immediately the order was placed, ending access to daily usage stats. I had downloaded the historical data the previous day, but now the only access I have to usage data is to phone BT. How very convenient when they have an issue with data usage being incorrectly attributed. They maintain the unlimited has been cancelled and it can take 5 days for this to be reflected in MyBT - here we are on the 9tth day and it still says unlimited ('My Package' tab returns an error message).
After hours and hours of wrangling, BT have come up with the same solution they seem to offer all customers who are victims of this issue - waiving their extra charges as a gesture of goodwill, and upgrading to unlimited broadband so the customer need never worry again. Not only that, but they are waving a magic carrot of a 'special deal' that means the unlimited package will cost 20% less than her current (capped braodband) package. Again, very convenient when it means that they then do not have to do anything about the original problem.
I don't believe that BT care who uses/has used the data. It is a drop in the ocean to them and it seems they can't be bothered / do not want to address whatever is going wrong. Switch everyone with this problem to unlimited (and hike the cost later probably) - hey presto, the problem is 'solved' for the customer, and BT can go on incorrectly attributing data usage, not worry about fixing that issue, and the customer has no idea whether it is ongoing because they can no longer see the usage figures.
Despite them offering a 'solution' I have chosen to escalate this complaint and intend to follow this through in the faint hope that perhaps a higher authority can force BT to disclose how many customers have been affected by this issue and maybe even require them to take steps to prevent this happening to others in the future. In my experience BT have been intransigent, unresponsive, and have given inaccurate information and failed to call back when promised. It took over a week to find a manager willing to take the complaint seriously, and to provide a response that differed from various reiterations of 'our systems are infalliable'. My mum stood no chance at all in arguing her case, and it has taken a huge effort and determination on my part to get this far. In short, they have made it as difficult as possible. Good luck with your own case - I will post updates when I have something to report.
