For NBA League Pass customer service, you can go to NBA.com’s support center. NBA League Pass support pages has FAQs regarding package choices, access, account management and billing questions.
You can submit an email question via the online form. To contact a customer service rep by telephone, you can call the phone number 1-844-622-8550 from 11:00 AM EST to 1:00 AM EST. The phone contact is not League Pass specific but hopefully they can help you with League Pass questions.