I am using Arduino Uno R3 with SIM900A (GSM/GPRS TTL UART MODEM - SIM900A (rhydoLABZ) [GSM-1965] : rhydoLABZ INDIA) .
The last problem was solved with the help of @HugoPT with the same shield - GSM Shield not taking Calls [SOLVED] - #4 by system - Networking, Protocols, and Devices - Arduino Forum
The problem that I am facing now is that I am not able to read SMS body Stored on the sim card. Everytime I query it gives different results, for example:
AT+CMGR=27
+CMGR: "REC READ","+91xxxxxxxxxx","","13/10/31,01:22:59+22",145,36,0,0,"+9198319"5
,i no negepornu ts,tsnwYfm
AT+CMGR=27
+CMGR: "REC READ","+91xxxxxxxxxx","","13/10/31,01:22:59+22",145,36,0,0,"+9198319,,
,s n aneeesn s ts,t egoem
AT+CMGR=27
+CMGR: "REC READ","+91xxxxxxxxxx","","13/10/31,01:22:59+22",145,36,0,0,"+919831011
ggb gs?rsgt st s egoee
This was after I changed :
AT+CSDH=1
OK
Before that when
AT+CSDH=0
the output was :
AT+CMGR=27
+CMGR: "REC READ","+91xxxxxxxxxx","","13/10/31,01:22:59+22"
So, this is going agseesnt st s, egoee
in which "So, this is going " was only a small part of very long test message. I've searched it everywhere but cannot find why this is happening. I also tried to search for any AT Commands to set the SMS Text mode parameters to show me a complete message but nothing is working. Please help! =( 
Please note SIM Baud Rate : 9600 , Arduino SoftwareSerial Baud Rate 9600 , Serial Baud Rate 9600.