Over my usage allowance - being overcharged

[#1]

At least 4 days before I reached my limit, I increased my maximum monthly overspend to £10 from £5. Yesterday I reached my maximum overspend limit (Used up my extra 10gb so in total 70GB) and my internet has been subsequently slowed to 256kbps as per the terms and conditions.
That would be fine, except on my front page it says my usage has been increased to 75GB and I will be charged £15 on my next bill. This is totally wrong because I am getting the reduced speed service (which is erroneous if my limit is indeed 75GB since I am under that limit) and I will be quite angry if I am charged an extra £5 for nothing.
Anyone had a similar experience? I need to know how to sort this out, hopefully it can be done here but I don't know.

[#2]

Go to http://portal.plus.net/upgrade_process.html?memberheader=upgrade and change to Unlimited. Unlike Extra there are no speed restrictions and you'll be paying £1 or £2 less per month depending on which Market your exchange is in.
You need to do that before your billing day. If you don't it won't take effect until your next billing date.

[#3]

To address the overcharge:
If you go to http://contactus.plus.net and look at your closed tickets you should find one that is something like this:

Quote

The customer has set £nn.nn Data Transfer Watch via the Data Watch portal tool.

The amount will be your basic payment plus the limit you have set. If you can find where you set it to £10 and there is no subsequent ticket changing it you should raise a ticket pointing that out.

[#4]

Hi Jelv,
Thanks for your reply. For the first part, I have already noticed the new unlimited package (I had to find it myself since it was never brought to my attention) about a week ago and have already changed to it, although my billing date is not until a few weeks time.
For the second part, I don't understand what you mean by your instructions, sorry. By a ticket I assume you refer to a customer service query ticket, but I haven't made one, and I can't see any way to make one or view existing tickets. I've checked 'manage my account' and it says there that my maximum overspend is £10. So I am being treated in one respect as though this is true, in that my speeds have slowed, but I'm also apparently being charged for an extra 5gb on top which is not right. Sorry to restate the problem but I am not happy about it. Any more help would be greatly appreciated, thanks.

[#5]

Go to here https://www.plus.net/wizard/?p=search and select closed questions in the last 7 or 30 days - depending on how long ago you made the change

[#6]

Hi deurone,
I have checked your account and can see that your Data Transfer Watch is set to only allow £10 of additional usage. As such you wont be charged for any more than this.
Hope this helps