I found this link: http://www.samsung.com/ch... In theory this should support Band 4 which is compatible in Argentina with 4G.

It seems nobody is able to confirm the LTE Bands that this model actually have :(

I'm afraid I don't know about the 5 minute call but I have changed from a Swiss to an Australian SIMM Card and have experienced no problems. Long Term Evolution (LTE): I cannot confirm which bands are used but the data transfer rate on the phone is sufficient for updates and gallery backups on Wireless and GSM networks.

Yes, a 5 minutes call has to be placed to unlock the phone. I dont know about the LTE Bands