If your dad's alright and able to eat then there's no need to call any one. I've got no idea what "hotline" would be interested or of any use. If your dad is not able to eat, then call an ambulance.
I'd go with the 9 jellybabies as advised by the doctor. But eating the whole packet won't hurt.
Once they are eaten, wait 10-15 min and test blood again. If over 4 have a longer lasting carb small snack, like a digestive biscuit or a glass of milk. If under 4 repeat with 9 jelly babies and then test again in 10 minutes.