Can you elaborate how did that work? I never heard about this method
So firms would advertize a missed call number on the radio.
People could give that number a missed call, and they would soon get a call back from the firm - thus never spending any money at all.
The more common interpersonal example was one person having more money than the other, or being on a company plan - so they would get missed calls from their family/friends, and they would then call back.
The cost was thus borne by the firm/richer person/person with more talk time.
Actual Example from my life: My dad had a cellular plan that had lots of free minutes of calling. So, I would just give him a missed call and he would call back. This was the early 2000s I think.
[1] https://academic.oup.com/jcmc/article-pdf/13/1/1/22316427/jj...
So eventually if you want to be profitable and sell more services, you have to offer a good price.
It's just the way it is. I even know people who look at fares and then decide if they want to take their own two wheeler or an Ola. Online food delivery works the same way. People hunt for deals and only order through that.
Sure some people pay for services. But those are generally rare.