Default SIM card faul

Hi everybody, after a long search I bought a wonderful lg nexus 4 on eBay, this phone had a broken touchscreen so I replaced it and it worked perfectly. After the reboot I noticed that my Sim card is not recognized, if I start the phone with Sim inserted on the welcome screen the touch become useless, instead if I insert the Sim later it's not recognized. I use this Sim in another phone and it works flawlessly, this morning I also bought a new Sim just to be sure but the new one isn't recognized too! I read somewhere that the problem was the metal folder of nexus 4 so the Sim needs to be insulated, I tried to do that but it didn't work too!I'm really upset the phone is really new it has a warranty yet!But I would like to solve this problem by myself to avoid to wait the producer fix it.I'm in Italy and I heard the fixing time are very long...Anybody can help me?I really appreciate it, thanks

Inviato dal mio Nexus 7 utilizzando Tapatalk