What to do with torn bill?

I have had this torn bill for a LONG time (years).. (about 85% intact.. missing left 15%). I have an image but Reddit won't let me attach it here. it came out of an ATM this way. I recently attempted to exchange it for a full bill at Citibank.. and they refused. They gave me some BS answer like "We either need both full serial numbers or one serial number and both full signatures." yet they could not cite a single bank policy stating such.

Furthermore, the Bureau of Engraving and Printing (BEP) says that in any case where more than 50% of the bill is present, it is NOT considered mutilated currency and can be exchanged at a commercial bank.

Two Citi branches have denied me now. I filed a complaint with their Executive Response Team and have not heard back in the calendar days that they promised me. I read online that if I fill out the form and mail it the BEP, that it could take a year or more to be exchanged.

Advice?