I feel like I just got my pocket picked! Opt customers into a smart cap... wait until their nice and comfy then increase the price by a few hundred percent then put the arm in! At least Dick Turpin wore a mask! Needless to say I will be moving to another provider asap. Not just for mobile but my broadband aswell.. total ripoff!!!
I'm sorry to hear you've had as higher than expected invoice and I apologise for the frustration caused.
You would be charged £0.10 per MB of data used over your tariff, you can of course chose to add a smart cap and change the limit to £0.00 so something like this would not occur. You can find more info on this here: under the heading "what happens when I go over my data allowance?"
My apologies this has made you wish to move providers for both your mobile & broadband services, if there is anything else we can help with please let us know.