Hey Pushkala,
The first thing I'm seeing is the imei buffer is set to 15 instead of 16 (which is what it should be).
I also don understand why the message is set to 141, that's very high.
As I'm much more of a hardware guy I would recommend testing your circuit, some buttons have two ins and two outs, if you're using both of the ins or outs then you'll just get a constant signal to the arduino to send.