Dont think you can give a bad reference by law now. They can refuse but not give a bad one.
Come on then own up. Who was the heavy breather on that call!? Haha
My missus is an administration manager and has to do references all the time,most companys now will just ask to score out of 10,timekeeping,attendance,attitude to work etc but they usually ask would you employ this person again so they can say no and why if they want to but unless you have stormed out,chinning the manager and smashing up his new jag,you should be ok