1998 - http://www.channelpartnersonline.com/articles/1998/12/paypho...
2002 - http://www.casa.ucl.ac.uk/cyberspace/requiem_for_the_pay_pho...
2008 - http://www.phonelosers.org/2008/09/pay-phones-are-doomed/
2010 - http://www.mnn.com/green-tech/gadgets-electronics/questions/...
2010 - http://www.cnn.com/2010/TECH/04/02/pay.phones.irpt/
2011 - http://www.phonelosers.org/2011/04/alternative-uses-for-pay-...
2017 - https://www.theatlantic.com/technology/archive/2017/02/objec... (Some are even ready to say they're already dead.)
From the perspective of computer history, pay phones are interesting because of their being the main host for phreaking subcultures. The best book on such is still probably Lapsley's Exploding The Phone: