Credit reporting agencies feel they have great powers to mindlessly ruin other people's credit. However, both the reporting agency (Experian, etc.) as well as the creditor (TXU) have affirmative duties to produce accurate reports. You can demand that they investigate apparently erroneous reports and if it doesn't fix the problem, yoiu can submit a statement of your own which the reporting agency is required to include in each report for a period of time. Failure to do that will allow you to sue them both under Fair Credit Reporting Act.
Lysbeth Goodman is an attorney licensed in the state and federal courts of California. This answer is for general information only and does not create an attorney client relationship between Lysbeth Goodman and any other person. You should schedule a consultation with an attorney to discuss the specifics of your legal issues.
As you have learned, neither creditors nor bureaus follow the rules regarding verification or "lack thereof". Rather than researching the dispute, the bureau automatically responds "verified". I am assuming you correctly made the initial dispute and attached evidence for the bureau to consider. The best evidence in this case would be a letter from TXU saying you never had an account with them.
Assuming you did that and the bureaus never changed your report then you need to follow up with a second letter "requesting a reinvestigation" of your dispute.
If your report remains unchanged after this, you send a third letter. In the third letter you tell the bureau they are liable for failing to conduct a reasonable investigation. A bureau does not violate the FCRA by not correcting the information - it violates the FCRA by failing to conduct a reasonable investigation. After pointing out the bureau is in violation of the FCRA, and you understand this, it is more likely the bureau will delete the TXU listing. (Notice I said "more likely", not that it will happen).
If the listing is not deleted, you should file suit against the bureaus.
Also, assuming you copied the creditor with all these letters (which I strongly suggest) you have a case against the creditor as well.
Do not expect the bureaus to correct the mistake on the first dispute. In my experience that almost never happens. You have to continue through the reinvestigation process or your dispute has no chance. Unless you have liability for failure to conduct a reasonable investigation it is unlikely you will get your credit corrected.
If none of this works I suggest contacting an attorney for assistance.