If you have a complaint about a company listed on the London Stock Exchange, they have a complaints department, and you can contact them online via www.fsa.gov or at the following address:
Regulatory Complaints & Enquiries
Trading Services
London Stock Exchange
Old Broad Street
London
EC2N 1HP
Telephone: 020 7797 3523
NASD have an online form to fill in on their website http://www.nasdr.com , and it's their recommended way to file a complaint against a company, though they do have a form you can print off if you prefer.
Sites are available for all the regulatory bodies so check out which one your chosen company is registered with, and follow their complaints procedure if necessary.
