Zendesk - Zendesk is a beautiful, lightweight help-desk solution.
HelpScout - Help Scout is a simple, straightforward way to provide excellent support
HiOperator - HiOperator is a virtual assistant that answers phone calls, chats with customers, provides in-app help, takes orders, and provides support.
HelpNinja - Simple & Affordable help desk
GetHuman - Find customer service numbers fast
SupportYourApp - Connecting talented people with the blooming IT industry to help them grow faster by outsourcing support.