Barclaycard and wrong default date

[Minder]

Hi, I wonder if anyone can help? I have just been given a default by Barclaycard for a debt that I was in an arrangement for and repaying each month but had a period of a few months during the summer when my income fell and I could only offer £10 nominal fee. I did contact them with my new proposal when I able to increase the monthly fee to £110 but all my letters and emails were not acted upon. As soon as I saw the default letter, I contacted Barclay to discuss as I have only just achieved a 'fair' on my credit file after a long period of debt repayment arrangements since 2008. The representative at Barclays put me at ease as he discussed the legal stance, he informed me that the default date has to be when the account was first in difficulty and that this date was showing 27/9/10 on the system and therefore the default we be on and removed immediately, thus not affecting my credit rating. He informed me to let it ride and discuss then the repayment of the debt. I contacted Barclay Sept and Oct by letter and calls but no response. I also rang again to discuss the default date and a second representative confirmed is would be 27/9/10 and that my previous call was clear with the notes on file. However, a default has now been added to my file with a random default date of 5/4/15! My score is now very poor and I will have to wait 4 1/2 years to rebuild my file. Any advise very welcome please!