Thanks aratti for the information,

Frankly speaking i did not have any idea what is DCE device, so i checked the internet and found that:
Typically, one is called DTE (Data Terminal Equipment) and the
other is called DCE (Data Circuit-Terminating Equipment). For instance, in EIA-
232 communications, DTE devices (terminals, PCs, mini-computers) are quite
stubborn and only want to talk to DCE devices (modems, multiplexers), and vice
versa. For this reason, you may connect a PC COM port to a modem using a
"straight through" EIA-232 cable. However, when you must connect a PC COM
port to another PC COM port, you must use a "null-modem" cable. The function
of the null modem cable is to "trick" the DTE device into believing that it is
talking to a DCE device by cross-wiring the data and control pins in the cable.
Ethernet AUI (Attachment Unit Interface) also uses the DTE/DCE convention,
However, itÕs not as simple as it is with EIA-232.
So in this case i think you meant: Microcontroller and mobile phone are both DCE device, so i need to cross-over RX and TX cables of the serial port.

I will try this asap and inform back the result, thanks a lot.