If a PlanetSim runs out of credit and is unable to perform a call, our service Zero Balance allows them to make an unanswered call towards another PlanetSim number and they are able to receive a call from another PlanetSim normally. Zero Balance is provided for free to all PlanetSim users. The user must be in a country with free incoming calls, otherwise there is a requirement of having enough credit for at least one (1) minute of call time is required. Please note the Zero Balance is not available in countries that are subject to extra charges.