I’m having this issue to, I have an email saying I’ve changed my plan for same data, calls and texts for fraction of the price yet for 2 months have been charged full contract price.
Even my account info/billing page agrees I should only pay £5 this month but another email says they’ll be charging me £40 soon. 

Hey there @Davies089, welcome to Community!

When you contract expires, it will continue running on the same contract at the same price until you upgrade/plan change, or decide to leave us. If you don’t do either, then we’d just presume you’re happy with your current plan.

@Webby1999, if you have any billing queries, please contact us via our live-chat:

https://www.idmobile.co.uk/live-chat

Thanks,

Tyler