Unauthorized account linked to my profile

I have been getting endless emails and calls from debt collectors with an account I have no knowledge of. The only account I have with them goes off on debit order without fail. When I went into my profile I saw an account I have no knowledge of and it's in arrears. Visited the Baywest branch only to be told an account that I DID NOT AUTHORIZE is set on my profile. The banking details are not mine and when I enquired as to WHY they would put this in my profile and the possibility of messing up my credit review as I will be blacklisted they simply said someone used my details. I was not helped at the branch and was told to call 081180 which I was not assisted as I held on only to be dropped. I need this removed from my profile as I did not authorize this.