Credit score ruined after disputed exit fee

Please can you help. I had to leave Virgin Media last year as had to move in with family while pregnant. I wanted to take my account with me but did not have a ‘home’ to go to. I explained circumstances to customer service and asked to waive the exit fee. They suggested i either force my family member to cancel their own broadband and take virgin media, or refer Virgin to the new tenants at the house I had to leave (no fault). In the end they agreed to put the account on hold to see if I could find somewhere to transfer it. 

fast forward a year and I am trying to apply for a mortgage, but have been declined. My disputed exit fee, while account was on hold, has been reported as 4 missed/late bill payments (I settled the payment at what I thought was the end of the hold period). Despite otherwise clean credit, it’s enough to scupper my chances of getting a mortgage and I’m now stuck. I am beside myself with stress. I have emailed credit file amendments but they won’t help. Is there anything that can be done? It will basically ruin me financially for 5 years.