A method of accessing a first communication system of a first communication provider via a packet-based network, the first communication system maintaining a first list of contacts being users of the first communication system. The method comprises establishing a contact-sharing channel with a second communication system of a second, partner communication provider, wherein the second communication system is accessible via an independently executable web-browser and the packet-based network, and wherein the second communication system maintains second group of contacts being users of the second communication system. The contact-sharing channel is used to fetch contact information of one or more of the second contacts, so as to display at least part of the fetched contact information in the client application and establish a communication based on at least part of the fetched contact information.