change "#define rxPin 0" and "#define txPin 1" to some other value may be "#define rxPin 2" and "#define txPin 3" for softwareserial (mySerial) since pins 0 and 1 are for the hardware serial which is used by the Serial monitor
change "#define rxPin 0" and "#define txPin 1" to some other value may be "#define rxPin 2" and "#define txPin 3" for softwareserial (mySerial) since pins 0 and 1 are for the hardware serial which is used by the Serial monitor