Is there a customer service phone number? AT&T Customer Service Phone Number 1-800-288-2747. AT&T is a communications giant that is the largest provider of mobile phone service and home phone service.How do you contact boost mobile customer service? Boost Mobile Headquarters Customer care Phone Numbers. The contact numbers +1-949-748-3200 and +1-949-748-3272 is available to contact with Boost Mobile Headquarters. The customers can also contact through company's Fax Number: +1-913-523-7727 whenever necessary.