Based on our record, KeepCalling seems to be more popular. It has been mentiond 2 times since March 2021. We are tracking product recommendations and mentions on various public social media platforms and blogs. They can help you identify which product is more popular and what people think of it.
Tello shares ownership with KeepCalling. KeepCalling's whole business is international calling. Source: over 1 year ago
As someone else in this post suggested, I also recently learned about KeepCalling: https://keepcalling.com/. Source: over 2 years ago
Asterisk - An open source telephony switching and private branch exchange service for Linux.
toolani - Cheap international calls
FreeSWITCH - FreeSWITCH is an open-source media application designed to support popular protools such as SIP and WebRTC and provides a platform to develop voice and video applications.
BNESIM - The all-in-one app for your communications. Voice, SMS, rooms, data SIM & eSIM in 200+ countries without roaming fees. Double data on the first top-up. Two years back-to-back winner of the "World Travel awards" for 2019 and 2020.
FusionPBX - FusionPBX is an open source FreeSWITCH GUI.
mytello - Cheap international calls via local dial in number at very attractive prices.