Originally Posted by hrcell
try to clean pin battery (on the battery not connector battery on the phone) and clean your sim card (used pencil eraser)
look your sim card have missing gold pin/gold line or not?
Not sure why doing anything with the battery would be in any way related with the SIM. I also forgot to mention that I had already tried cleaning the SIM card at the start with alcohol. In any case, the SIM card works fine in another phone, so it appears that there isn't problem with the SIM card. In any case, I managed to RMA the phone, now the long wait to get it back...
Siemens A57 -> Nokia 3110 Classic -> Samsung Omnia SGH-I900 -> Samsung Galaxy S2 GT-I9100 -> Samsung Galaxy S3 LTE GT-I9305