While both versions of iTouch can use OSCall, there are some limitations.
Call Method of iTouch 4
A) Use earphone to call.
B) Call without use of earphone (note: the loudspeaker of iTouch 4 is installed in the lower right corner at the back of the device).
Call Method of iTouch 3
C) It can make calls only by using the earphone（iTouch 3 has no MIC，if not using an earphone,there will be no speaker end）.