system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: How does dominos pizza have a single number to call the most local place, while their landline number is much different?
gpt
Back in the day, people had to pick up the phone and ask the operator to switch their call to the person they wanted to talk to. Now these jobs aren't done by people, they're done by machines in which we enter phone numbers into.

What's happening at your pizza place is pretty much the same thing that killed the operator - the call is being routed by a computer in a call center.  Here's the basic steps:

1.  Computer receives the call but does not answer.
2.  It uses your caller ID information to determine your location.
3.  It starts a new call and dials the local shop.
4.  When the local shop picks up, your call is immediately answered and connected to it.  
5.  When either you or the shop hangs up, both calls the computer is dealing with are ended.

This makes it *look* like you called the local number, when in fact both you and the pizza place are actually talking through this call center.  You can imagine this "connection" to be like holding two phones together, mic-to-speaker, so other people can talk.