This is a collection agency that uses several numbers, all beginning with 405-555-(2621, 2625, 2638, etc.).  I never speak to them, but I have a portable landline phone whose base is a speaker phone.  When I see their number on Caller ID, I turn on both phone and speaker simultaneously and the feedback noise is incredible!  Suffice it to say they don't call as often as they used to....

LOL. That is truly awesome.  I've been getting calls from "405-555-XXXX" numbers on my cell phone something fierce for months as well, I figured it was a collection agency of some sort and I'm glad you've confirmed such. I just wonder what they're trying to collect for...I can't recall anything I've not payed.