Sim800: CREG:0,1 but CGATT:0... ALWAYS

hi community, this is my first post, i hope that somebody can help me with my issue.
i’m using a sim800l with arduino uno, i’m sure that the alimentation is correct because using another module my issue disappears.
well, this is my problem: sim800l is connected to the gprs, in fact the led blink every 3 seconds and “AT+CREG?” answer to me “CREG: 0,1”, but the command “AT+CGATT?” always answer “CGATT: 0”. i will be very grateful to anyone that try to help me, good work to all :slight_smile: