Thanks for your help. So these guys can't do anything? Does this mean EDF have sold the debt on? Does this affect my credit rating or anything like that?

Good evening, I received a letter today from EOS which I think relates to an unpaid EDF bill from 2 years ago. When I moved into the previous propety I informed EDF that the account holder had changed over to my name. For the 18 months that I lived there I never received a letter addressed to me from EDF only letters to the previous occupier. About 18months ago I gave EDF my new address and said that I would pay the amount outstanding. This was all over the phone and I was told that as it was an old style account it may take up to 6 weeks to receive the bill. A bill never appeared at my new address either. EOS are now sending letters and making numerous phone calls to my mobile number. I've not answered any calls but in concerned I'll have one of their representatives turn up on my doorstep. As no contract was ever signed and when last speaking to EDF on the phone I was willing to pay the bill where do I stand? Any help would be appreciated.