Poor Service and not my problem solving

I app**** for a Fibre line on 25th November 2022, Black Friday. They told me it takes abou 7 to 14 working days. I waited and waited. After the time period I wanted to know what is going on, they told me the previous owners line is still active and therefore they cannot put a new line in as the previous owner should first cancel their line and contract with the address. What is frustrating is that now I must wait the previous owner? How am I suppossed to track down previous owner and tell them they should cancel their contract? It is not my job to search for the previous owner and wait for Supersonic to track him/her down. All Supersonic has to do is put in a new line at my home. The contract between Supersonic and the previous owner has nothing to do with me. Now I sit without wifi and cannot work or do anything. I think it is really poor service to say I cannot get my line because of the contract with previous owner.