Twice as fast as what?

As NOT using digit dialing!

Phones were around for a long time before you could just pick one up and dial a number of somebody halfway across the country to call them like magic. That's a fairly newfangled way! Before that, there was no direct dialing. An operator at a switchboard at the phone company had to physically plug a cable to connect your phone line to your callee's phone line. You had to talk to the operator to ask them to do that!

In the very early days, you would ask for the other party by name, and the operator would look up the right jack that way. Eventually, there were exchanges, and you might ask for a particular party at "Garfield 7", or "Madison 3". Those are the names in the Allan Sherman song I linked below, that he is complaining about losing due to the move to digit dialing. Which is also what this ad is about - trying to get the public on board with it.

Digit dialing was not totally rolled out until the 1960's, although it was partial before that. New York City had switchboard operators in the 1880's. So the way you are used to, of simply entering a number to reach someone, has been the universal method for much less than half the time telephones have existed!

Editing, here is a photo of switchboard operators plugging cables in the 1950's. But clear back in the 1880's, it happened like that, but more primitive of course than the 1950 photo here.