These contacts must only be in the contact list of the cell phone to participate in the calls. So you won’t need to add them or register on any of the platforms run by Facebook. According to the company, CatchUp’s goal is to combine the conventional format of phone calls with the ease of a dedicated app (which differentiates it from WhatsApp and other popular messengers). This is because people are not always comfortable or available for a video conference. Despite the opportune moment, CatchUp was not created as a means of communication due to the coronavirus pandemic. However, for this reason, its launch was accelerated to meet this type of demand.
