You can resend it via fax but make sure that you are stating your point exactly how you would have done it online if it was possible to make that entry. Type your dispute as a letter and if you have any documentation include a copy of it as well. If you fax and mail, they (Cra's) may start working on the faxed one and get it resolved but then get your mailed dispute and this may cause you to have a hold up in the final processing of it.
It can't hurt either to gw the OC. I just sent 4 letters off to my OC's who are all listed on my BK7. They may turn me down, but I wanted them to know my real story and what happened and why I did what I did. Might get earlier deletes of those derog accounts or not.. They are coming off next year anyway.
So, refax and if you want, your decision, get a fax for the OC (I did with JCPenneys and it worked, got a delete for dh), and send them your letter.
Worth a try.
Good luck
Eve