My phone sometime misses phone calls even the signal is good, and it won't show any missed call. It has been bothering since I got the phone because I really have no idea who called me and they'd be mad at me because they thought I didn't answer and didn't call them back. I have no idea if it's the problem of my phone or it's SIM card problem. Nokia costumer service suggested me to hard reset the phone but it didn't solve the problem. Is it possible to have my phone replaced because of this problem? I think it's kind of hard to prove them this problem because it does not happen all the time, it just happens occasionally.