Written notification about debt: Debt collection

According to 15 usc 1681 I have the right to dispute inaccurate and unverifiable Information that's on my credit report. I disputed multiple times with credit bureaus and it's coming back as updated and verified without a proper investigation. The company failed to send me any of the information I requested even with my further complaint they never sent verification of debt, the ORIGINAL Contract bearing my signature & explanation of the amount and how it was calculated.