I want to know if the SIM800L works on US soil? I can´t get it to work on the H2O network! Does it work wit ATT or I only need the APN settings? If so what are the commands for data connection and configuration? Does the SIM800C works then?
Both SIM800C and SIM800L (you mention both modules in your question) are compatible with the US GSM networks. It is not possible for me to tell if H2O or AT&T have GSM coverage whereever you are trying to use the module. AT&T is planning to shut down their GSM network by the end of 2016. If you issue the
AT+COPS=? command, the module will list all available networks at your location.
Documentation on the commands required to handle voice calls, SMS or internet connections can be found in the 'SIM800 Series AT Command Manual'.