Unsatisfied

I went to buy a cellphone at jet chrishani mall and was told I needed to buy a Sim card which I didn't have a problem with, the problem was when they said I also need to buy 29rand airtime to activate the Sim and had to put that airtime on the new Sim card. 1 I don't understand where this rule comes from 2. Even exact does the same thing I'm very unsatisfied. They ended up selling the phone to me because I decided that I will go to another store that won't tell me about airtime.