Single Number Call Center is a simple call center with only one phone number. The number is used both for agents and customers. First a calling user is asked about a role - customer or agent and suggest to press “1” or “2” respectively. If the user is a customer the call is placed in a queue of customers' calls. If the user is an agent then the call is connected to the first customer call in the queue. If the queue is empty the agent is informed and suggested to wait for the next customer or leave the call center. The call center is built using Twilio API . To play with the demo there must be at least two callers (and two phone numbers) - one in a role of agent and another one as a customer. Of course, there may be several agents and several customers. To start playing with the demo use the toll free number (866) 960-9866. Enjoy!