Indycall Booster gives you an option to have more free airtime.
To get the free airtime, Indycall Booster gives you various tasks from the advertisers. Comple these tasks and get free IndyMinutes.
Use these minutes in the Indycall app.
With the IndyMinutes you have longer free calls and in-app advertisement is removed from Indycall.
You can alsoo buy credit in Indycall Booster