In most settings that question includes an implicit "cell"! They're not asking if they can go home with you and use your landline, they're assuming you have a p

In most settings that question includes an implicit "cell"! They're not asking if they can go home with you and use your landline, they're assuming you have a phone in your pocket with service. A landline is a type of phone in the same way that a panda is a type of bear. Technically it's true, but if you say you went to see the bears at the zoo it's your own fault that people aren't picturing something with black and white splotches.