Birthday Reminders still showing up despite being unticked? (Outlook Calender)

Hi, I have my Windows 8.1 Outlook calender synced with my iPhone (linked through my hotmail address). The reminders for one always show up on the other when they are synced and on wifi which is great. However there is one main problem. The birthday calender under the outlook section and also under the main section are unticked. But I still seem to get notifications at midday every day about whos birthday it is the following day. This is annoying as my outlook is linked to everything, i.e multiple inboxes and facebook etc so I get a notification from pretty much every single contact I have. This also is annoying when using siri to create and event as at the end he will say 'there are already 7 events lined up for today which overlap do you wish for me to proceed'. That 7 being the birthday reminders. I dont know if this is a small glitch or what but it is starting to get really annoying. Any advice would be great!

Thanks.