You can call their toll-free Thriftline at 877-968-3778, Monday through Friday, from 7 a.m. to 9 p.m. ET. There is also an international phone line at 404-233-4400 that is not a toll-free line. The TDD (Telecommunications Device for the Deaf) line for the hearing impaired is 877-847-4385. The general mailing address is Thrift Savings Plan, P.O. Box 385021, Birmingham, AL 35238. If you have an online account, there is a Message Center that allows you to send and receive messages. Response time is two business days. Finally, for specific inquiry categories (loans, death benefits, court orders, federal tax levies, press requests, and more) there are individual post office boxes and/or email addresses listed on the TSP website.