Hey, I have an Arduino Genuino/Uno board, connected with bluetooth, and anytime that I send an ASCII Character to the board, it is being misinterpreted and transformed into an "unknown" symbol.
What is your setup? Serial Monitor <---->UNO <------> Bluetooth Module <-----> Android Phone. Is it correct?
You send a character (say A) from Android phone and it does not appear correctly on the Serial Monitor. Is it this problem? If so ( as suggested in Post#1), check for the matching baud rate between Serial Monitor Window and your sketch (Serial.begin(Bd)).
Please, post your codes with code tags (</>).