iPhone 5 connecting to internet periodically.

Had an iPhone contract for 3 months now, first month normal bill. Second month £60 extra charges

Third month £63 extra charges.

They are all from mobile data being exceeded. Looking at my bill my phone is constantly connecting to the internet every hour 00:49/01:49/02:49/03:49 and this carries on all day every day.

WiFi assist OFF

Background App refresh OFF

No email account even active on the phone so no push emails.

Wracking my brains as to what my phone is doing and why is costing me so much!!

Any help?