In my home country of Bulgaria, we used to do that all the time.
It works because most phones are pre-paid. You don't have a monthly bill. Instead, you preload $10 - $20 into your SIM, and you can text at $0.20 per SMS or talk at $1 per minute. Also, only the person that initiates the call or SMS pays, the receiver is not charged anything.
You'd still need at least a balance of $1 to initiate calls, so when people's balances get low, they only call people and hang up immediately (we call that clicking / buzzing).
Essentially you make plans to meet somewhere or go out, and you click / buzz the other party when you are ready. It is generally understood that if you get a click / buzz, you should look around or call that person back if you have a higher balance ;)
Also with the preloading SIM card payment model, you can essentially have a $1 balance on your SIM card for a year, and receive calls without paying anything.
"I am not sure how well this would work in the US as apparently you can be charged for inbound calls there."
Right, in the U.S. you're charged for "air time" on both outbound and inbound mobile calls. However, the trick would work with land-lines, and is especially useful when one party has a calling plan with flat-rate monthly billing and the other pays per-call. I had some family members who did this many years ago, long before there were mobile phones.
Answering machines (for land lines) are also designed to exploit the "missed call" trick: if I call my home answering machine to remotely retrieve my messages, it will answer on the first ring if I have messages, otherwise it will answer on the fourth ring. Thus, if it rings twice, I can hang up, having learned that I have no messages without having paid for a call. (Even if I'm calling from a mobile phone and paying for the call, I've spent much less time to find out that I have no messages.)
The only problem with this scheme is that it's somewhat unreliable. The "ring tone" that the caller hears is generated by their local exchange, and doesn't exactly correspond to the ring on the callee's phone, which is generated by the remote exchange. So the caller may hear a ring tone and hang up before the callee ever hears a ring. (At least that's the way it works in the U.S.) So it's probably more reliable to hang up after the caller hears two ring tones.
Back in the '90s, we used to pass messages around from payphones for free by stuffing them in the name recording on automated collect call authorization systems.
We'd call the 800 number or dial 0 to setup a collect call and when the machine would prompt for a name, we'd stuff the message. The end result was the recipient receiving an automated phone call that would announce: "Hello. This is Pacific Bell. You have a collect call from WEREATTHEBEACH. Press 1 to acc..."
It works because most phones are pre-paid. You don't have a monthly bill. Instead, you preload $10 - $20 into your SIM, and you can text at $0.20 per SMS or talk at $1 per minute. Also, only the person that initiates the call or SMS pays, the receiver is not charged anything.
You'd still need at least a balance of $1 to initiate calls, so when people's balances get low, they only call people and hang up immediately (we call that clicking / buzzing).
Essentially you make plans to meet somewhere or go out, and you click / buzz the other party when you are ready. It is generally understood that if you get a click / buzz, you should look around or call that person back if you have a higher balance ;)
Also with the preloading SIM card payment model, you can essentially have a $1 balance on your SIM card for a year, and receive calls without paying anything.