EA7KGO EchoLink support is available in (currently beta) firmware v39. You can enable beta firmware upgrades on the Settings page, Firmware upgrade section. Make sure Advanced mode is enabled at the bottom right of the web interface.
EA7KGO EchoLink uses RTP and RTCP UDP packets for communication, which is a commonly used protocol for VoIP. Cell phone providers may filter these RTP/RTCP packets to force you not using VoIP and instead use (and pay) for regular phone calls. Try contacting your provider and explain them your issue.