Have you ever used a phone booth?

yes, many times

I knew someone many years ago who had an older brother who walked into a hotel lobby and then walked out... with its phone booth. It was a prank or a dare or a pledge or something.

Not a booth, but [taken from Wikipedia article on J. Paul Getty]

Getty famously had a pay phone installed at Sutton Place, helping to seal his reputation as a miser. He placed dial locks on all the regular telephones, limiting their use to authorized staff, and the coin-box telephone was installed for others. In his autobiography, he described his reasons:

Now, for months after Sutton Place was purchased, great numbers of people came in and out of the house. Some were visiting businessmen. Others were artisans or workmen engaged in renovation and refurbishing. Still others were tradesmen making deliveries of merchandise. Suddenly, the Sutton Place telephone bills began to soar. The reason was obvious. Each of the regular telephones in the house has direct access to outside lines and thus to long-distance and even overseas operators. All sorts of people were making the best of a rare opportunity. They were picking up Sutton Place phones and placing calls to girlfriends in Geneva or Georgia and to aunts, uncles and third cousins twice-removed in Caracas and Cape Town. The costs of their friendly chats were, of course, charged to the Sutton Place bill.

In a 1963 televised interview with Alan Whicker, Getty said that he thought guests would want to use a pay phone. After 18 months, he said, "the in-and-out traffic flow at Sutton subsided. Management and operation of the house settled into a reasonable routine. With that, the pay telephone [was] removed, and the dial locks were taken off the telephones in the house."

I've never used a phone booth myself. And just to clarify I am indeed talking about phone booths and not just pay phones.

In the late '90s and very early 2000s, there were still a few phone booths scattered around Los Angeles. There were even some at LAX as late as 2013 or so.

Nowadays, the only ones I know of are located in the backs of lounges and hipster-type bars, serving as nostalgic art pieces of sorts.

And like this non-functioning one on the street.
https://fotospot.com/attractions/california/red-phone-booth

I never saw a full sized phone booth that you would completely get inside. We just had these privacy shield things on either side of the phone.

Yeah, they were disgusting. The phones stunk of other peopkes bad breath.

Many times. I grew up in the 70s.

Sure, but only for traveling through time.