I've just talked with the live chat and technical help on the phone, and nothing! I changed carrier from Telstra to Optus ten days ago, and I can't use the 4g. When I search for networks, the Yes Optus 4G is not available, and previous to Optus, I had excellent signal anywhere with Telstra. Now I CAN'T even load a picture on instagran. Anybody, any ideas?