Haha I've done this before, god I hate the 'sickie' phone call! Pro tip: call early just before opening hours when you know your manager isn't there, then you can send an email instead: "tried to call earlier but couldn't reach you, I'm taking the day off sick" etc. etc. Embarrassingly I have used this tactic on many occasions. It deeply saddens me that I have to resort to such childish behaviour.