United is HQ'ed in Chicago, IL:

Mailing address of Customer Relations is:
Customer Relations—WHQPW
P.O. Box 66100
Chicago, IL 60666

Tel
Customer Relations
1-877-228-1327 (Toll Free)
Fax: 1-877-406-1059 (Toll Free)

If you still don't get statisfaction, as a last resort you can try bypassing CR:

United Corp Office main number
Ph: 847-700-4000
Ask for the office of JOHN W. CREIGHTON, Jr. Chairman and CEO UAL Corp and United Airlines


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Michael Steinberg
Editor
BizTrip
http://www.biztrip.com