Big charges for Broadband Phone - but I don't use it!!!!

[#1]

I happened to look at my account activity this morning, the 30th of November.  A new billing month has started today, presumably from 8am.  It is now only 9:30am but my usage is saying I've already used 9.9MB!  Of that 39% is 'Broadband Phonecalls' and 42% is 'Other'!!  I never use Broadband Phonecalls, which assume is Skype, etc?  What on earth is going on?

[#2]

9.9MB isn't a lot of data and is more than likely just browsing and background usage.
Your usage resets in the early hours, usually around 5am, so any usage after this time will count towards this month.
It's worth noting the information on the View My Usage page here:

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Please note: Occasionally you may see usage in a category that you haven't used (typically a few KB or MB). This is almost always background traffic that our systems have classified incorrectly and is nothing to worry about.

[#3]

But why is there anything at all under the category 'Broadband Phonecalls'?

[#4]

And where can I check what I have been charged for 'Broadband Phone' in past months?  Usage History doesn't let me see the breakdown.
I am very concerened as in all the time I have been with Plusnet I have never gone over my monthly usage limits but for some reason this has started to be the case in the last few months.

[#5]

You can check a breakdown of any bills from here: https://portal.plus.net/my.html?action=view_transactions&s=0

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why is there anything at all under the category 'Broadband Phonecalls'?

My guess is that it was another type of usage that has been incorrectly categorised as broadband phone.
IMO I'd not be too concerned unless this escalates and more usage appears under that category.