OneSim VoIP is a Mobile app provided by OneSimCard and its parent company Belmont Telecom, Inc. OneSimCard is a pay-as-you go GSM-based international cell phone service provider that was launched in 2007 and offers voice and data services to users to help lower global roaming costs for those traveling abroad.
OneSim VOIP is available for both Android and iPhone that makes calls at very low rates when connected to a Wi-Fi network. Currently, OneSim VoIP is available only for phones which use Android OS 2.0 and higher or Apple iOS 4.0 or higher, including iPhone, iPad, and iPod Touch.
The VOIP service was introduced to allow users to make even cheaper calls via Wi-Fi than through standard cellular networks. For customers who also have a OneSim VOIP account, calls to other OneSim VOIP account holders are free as long as the OneSim VOIP account is currently active.