Not quite sure why you've been advised of 90 days for a decision to be made about potentially incorrect credit file data @TTYTT, as it certainly shouldn't take anything like that long. I'm assuming you've emailed creditfilereferrals@o2.com? Their SLA is to respond to you within 5 working days, so you should be hearing back from them very shortly all being well.
It can take some time for what you see on your credit file to update, but this is often caused by third party credit file services which only "refresh" the data you see on a monthly basis - so if it takes for example a month for O2 to load new data directly with the CRA, and then a further month for your provider to generate a new report including the newly uploaded data, this can result in a considerable delay - although lenders should always have access to the latest data loaded with the CRA's.
One important question is whether you made use of the sim card supplied with the phone at all before it was returned to O2? As if you did, even though you are perfectly entitled to cancel the contract within 14 days you would still be liable for any usage charges incurred - I realise it's unlikely that you spent £21 in just a couple of days, but thought it worth mentioning as this could be the cause of the issue.
Depending on your lender (and I do speak from personal experience here), they will sometimes overlook such a small default so long as it's satisfied, therefore regardless of any dispute over the amount and whether it's owed it may be beneficial to make the payment and obtain confirmation that it's settled, with a view to disputing it further once the mortgage is sorted.
Just a few thoughts for you, in case Martin isn't able to work his magic in the meantime.
I work for O2, however any advice or opinion given in this community should be considered my own and not necessarily representative of Telefónica UK Limited.
