Urgent: Final Demand Received Despite No Outstanding Balance

I’ve just received a final demand letter in the post today stating that I owe £20 and that the debt will be passed to a collector if unpaid.

This is the first letter I’ve received—no prior communication or reminders.

To be clear, I do not have any outstanding payments on my account.

Here’s what I can see on my payment history:

• 23rd May: A £10 payment failed but was re-attempted the same day and successfully cleared.

• 2nd June: Another payment (requested early—it wasn’t due until the 25th) also failed but was again re-attempted that same day and cleared.

• There’s always money in the account, plus an overdraft, so I don’t know why it failed in the first place.

Despite this, when I checked my iD Mobile account, it bizarrely showed that I owed £20—yet there were no outstanding invoices. Even more confusingly, it also claimed that my next bill would be £30.

My plan is a SIM-only deal at £10/month, which has been out of contract for nearly two years. I also have a £12 spending cap, so how could my next bill possibly be £30?

Before I realised there was no actual outstanding amount, I went ahead and paid the £20 shown—twice, in fact—because it didn’t register the first time. That left me £40 in credit. After the supposed £30 bill was taken, I’m now £9.99 in credit.

I’ve spent hours trying to resolve this through live chat with no success. I genuinely don’t know what else to do.

Frankly, this is unacceptable. Receiving a threatening final demand over a non-existent debt is incredibly stressful—especially when it’s accompanied by warnings of debt collectors. We've all heard the horror stories about collection agencies turning up at the door or making demands with their ridiculously high added charges and threats to take goods to the value of!!.

Please investigate this urgently, confirm there is no debt, and provide a written explanation of how this happened. I’d also like confirmation that this has not affected my credit report in any way.