Yes I still have the SIM searching continually problem. When switching the iPhone 6 off and on the message "SIM locked" appears and after entering the unlock code the "SIM searching" message appears in the top left corner of the phone. I think I need another swap SIM from Virgin Mobile but there is no way for me to make contact with them at present. I have been paying the monthly charge for several months with no service. I am not happy.
I tried the sim with another iPhone 6 and it said "no service". Oddly, the sim back in the "new" iPhone 6 also said "no service" rather than "searching". I guess I have to get back to the supplier of the phone unless you have a better idea.
The handset was purchased from a third party. The sad story is that my son Tim who was in my family group died from cancer in March and I was attempting to include my daughter Kate in the group instead of Tim. Unfortunately Tim's phone was damaged when he died so I had to buy another one.
Having checked Apple Support I have now looked at Settings - General on the iPhone 6 that keeps searching and I see that The Carrier is Virgin 3.6 but the Network is Not Available. It seems to me that the phone is not Network Locked but can't find the Virgin 4G signal. Maybe I do need a new sim.