The helpdesk handles direct links for assistance when encountering issues related to your account of exchange. Most intermediaries have Frequently asked Questions (FaQ), knowledge base, a support-team for technical and financial assistance, e-mail support and ticket systems all which are used for problem solving. Though every exchange handles customers and/or clients different.
Founded: 2014 by Arthur Hayes, Ben Delo, and Samuel Reed.
BitMEX stands for Bitcoin Mercantile Exchange. It is a peer-to-peer trading platform that offers leveraged contracts that are bought and sold in Bitcoin. It has above-average support rating, including e-mail and ticket support, a knowledge base and chat features. They also got multiple social media channels.
Founded: June 2012 by Brian Armstrong and Fred Ehrsam.
Coinbase is a digital currency exchange headquartered in San Francisco, California. Coinbase has a very extensive knowledge base. Most standard requests will probably find an answer there. If you are submitting a support ticket via email, expect a response within 48-72 hours.