what is the syntax of at*psstk="get input"?

AT*PSSTKI=1
OK
AT+CMGF=1
OK
AT*PSSTK="SETUP MENU",1,1
OK

*PSSTK: "END SESSION"
AT*PSSTK="GET ITEM LIST",8
*PSSTK: "GET ITEM LIST",1,1,4,"Top-Up Customer",0,0,0

*PSSTK: "GET ITEM LIST",2,2,4,"Top-Up Retailer",0,0,0

OK
AT*PSSTK="MENU SELECTION",1
OK

*PSSTK: "SELECT ITEM",1,4,"Top-Up Customer",0,0,1,0,0,6
AT*PSSTK="GET ITEM LIST",6
*PSSTK: "GET ITEM LIST",1,1,4,"Balance Transfer",0,0,0

*PSSTK: "GET ITEM LIST",2,2,4,"Balance Inquiry",0,0,0

*PSSTK: "GET ITEM LIST",3,3,4,"Last Transaction",0,0,0

*PSSTK: "GET ITEM LIST",4,4,4,"Check Trans ID",0,0,0

*PSSTK: "GET ITEM LIST",5,5,4,"Change PIN",0,0,0

*PSSTK: "GET ITEM LIST",6,6,4,"U-Top Up Help Line",0,0,0

OK
AT*PSSTK="SELECT ITEM",1,2,0,0
OK

*PSSTK: "GET INPUT",1,0,4,0,4,"Enter Customer Mobile Number",0,0,255,"",11,11,0

*PSSTK: "GET INPUT",1,0,4,0,4,"Enter Top-Up Amount",0,0,255,"",2,4,0
AT*PSSTK="GET INPUT",1,4,"03425100762",0,0
ERROR

plz tell me the exact syntax of get input so that error didnot occur
Thanks