Pco holdco s.a.r.l default

Am looking for some advice on how to deal with this company after checking my credit file to find they have default against me. I had never heard of this company.
I entered into an iva on 7 oct 2013 and completed on 7 december 2015. After some digging it looks like barclaycard had sold my debt to them.how do i go about getting this default removed from my files?contact barclaycard or try and track down pco holdco?have searched online but no currect address for them,just old ones

Thanks in advance