Contact Merrill Lynch customer service. You can call at Merrill Lynch toll free number (866) 706-8321, write an email, fill out a contact form on their website www.ml.com, or write a letter to Merrill Lynch And Co, Inc, 222 Broadway; 17th floor, New York, New York, 10038, United States. Client Relationship Agreement - Merrill Lynch A Merrill Lynch Cash Management Account® (CMA® account) is a securities account that ofers access to a full range of investment products and services. Trough a CMA account, you can invest in almost any kind of security available, including stocks, bonds, mutual funds and options.