I send SMS successfully from the SIM900 and the SIM5320 val. The problem is that each SMS deduct credit from my airtime balance. I have SMS-bundles loaded and have tried 3 different mobile companies SIM cards, but all only deducts my airtime at 0.85c per SMS. I used the AT command sendATcommand("AT+CMGF=1", "OK", 1000); // sets the SMS mode to text.

Any suggestions?


  1. Regarding the cost of text messages, I use two companies for my SIM. 1. Alarmsim and Truphone. Alarmsim is .15 cents per outgoing and incoming is free. Truphone is .09 cents outgoing and incoming is free.

  2. Are you including the SIM900.h library? If you do then your void loop command is:
    Where “CELLNUMBER” is the number of the cell phone you are sending to, be sure to include it in international format if you are using a Truphone SIM i.e. +15551212. “TEXTOFMESSAGE” is what you are sending.

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