Vodafone - Ignoring Complaints & Defaulted Payment on Credit Report

After reading the forums about how Vodafone are ignoring complaints i cant believe how many people are in the same situation as me.
I recently found out i have a defaulted payment on my credit report from Vodafone saying i have not being paying a fee of £23 for 2 years, when i cancelled my contract with them 2 years ago and they are claiming this is a termination fee. I have phoned countless times, spoke to someone on online chat who confirms in writing the charge should not be there, i have went into various branches and they have also said they cant see why that charge is there as my account is closed, I have been phoned and told the problem is sorted and should reflect on my credit report within 4 weeks - its still there, i have completed online complaints as well as writing a letter to customer relations manager, which has been completely ignored. I am understandably very frustrated. I now have a mortgage but i had been rejected by 2 lenders because of this being on my credit report. I need it rectified ASAP on my credit report as any future credit is being rejected because of this. Im reading that Lee from Vodafone Comms team has been helping people in similar situations to me, I have tried everything else and don't know what else to do so have resulted to writing in this forum as my last hope! Lee can you please get in touch with me.