PNP transistor turns on at 3.3v
I suspect you are trying to drive the PNP base with a 3.3V logic signal while controlling 5V to the buzzer. That just isn't going to work. To turn the transistor off (non-conducting) you need to raise the voltage on the base to be close to the emitter voltage, or about 5V. You can't do that with a 3.3V logic signal. You make a PNP transistor conduct by lowering the base voltage about 0.7V below the emitter voltage, not by setting the base voltage to 0.7V above ground.

You might be able to add a pullup resistor from the base itself to 5V to turn the transistor off when the logic output is 3.3V. Select resistor values so that when the 3.3V signal is low the voltage at the base is less than 4.3V. You would also have to select resistor values that limit the current that will flow back into the 3.3V logic output when that output signal is high. This is all just speculation, you haven't provided a datasheet for the device that is driving the base.