GSM wont sent the message

my coding is simply if smoke is detected, the relay will be ON and GSM Module (900A) will sent the message. but when i test it on a complete circuit with mq-2, relay module and GSM module 900A, the only thing that functioning is the smoke detector and relay. can anyone help me as this is my fyp. im also new to coding so im suck big time

relay__smoke_and_gsm.ino (1.51 KB)

relay__smoke_and_gsm.ino (1.51 KB)

coding.pdf (62.4 KB)

If you could post your sketch (es) within </> code - tags, we can have a look.