dfrobot v3 bluetooth module

hi,
i've bought a dfrobot v3 bluetooth module to connect to arduino MEGA 2560.
i was able to connect it to Arduino using TX and RX pins and to connect it to an android smartphone.
Then i used the serial monitor to communicate with smartphone.
The Serial monitor was able to send letters to the smartphone, but when i tried to send letters by smartphone to serial monitor it didn't receive anything.
connection: pin 16 (TX2) to RX module
pin 17(RX2) to TX module
BAUD RATE: 9600
i even tried to switch RX and TX pins, but it doesn't communicate on both sides.
can someone please help me?
i've bought a dfrobot v3 bluetooth module to connect to arduino MEGA 2560.
i was able to connect it to Arduino using TX and RX pins and to connect it to an android smartphone.
Then i used the serial monitor to communicate with smartphone.
The Serial monitor was able to send letters to the smartphone, but when i tried to send letters by smartphone to serial monitor it didn't receive anything.
connection: pin 16 (TX2) to RX module
pin 17(RX2) to TX module
BAUD RATE: 9600
i even tried to switch RX and TX pins, but it doesn't communicate on both sides.
can someone please help me?