Why does my iphone 4s use so much mobile data?

With my old blackberry i would never use over 100mb a month, now i have a iphone 4s i haves used nearmy 500mb in 5 days, why is this? How can i use less? (and yes i already use ovano)

Sounds like there are apps that constantly send and receive data.

I don't have an iphone, I have an android phone but I keep the Wi-Fi on and mobile data turned off unless I really need it.

It may be due to an applications running in background.those applications continuously needs internet to update such as stocks, world time etc. You may close those apps in app manager.

I have the exact same problem, my mobile data goes for no reason, so this what I started doing many months ago and It helped:
- I turn of mobile data unless I really need it
- I learnt that watching videos on the Internet for even 5mintues will take like a 100mb no joke - its happened many times to me, I dot think this happens with YouTube

Why that may be happening to you:
- apps are using the mobile data in the background
- you may be downloading stuff with you're mobile data on which will kill you data like mad so use wi-fi for that

USE wi-fi most of the time and leave that on as you're normal Internet connection

This may be due to the apps you have downloaded on phone. Some apps use mobile data for them to function regularly. Even, when you are not using them, they continuously collect mobile data while you are not aware of it. Most apps that use push notifications and map or location services rely on mobile data to function properly.
To minimise your use of mobile data, try the following things:
- Make sure you properly understand details of all the apps on your mobile.
- Delete the ones that are unnecessary or the ones that you don't use at all.
- Connect your mobile to a Wi-Fi network when at home or office.
- Reduce the use of online messaging services, such as Skype, Vibre, Tango, Whatsapp etc.
Alternative, you can purchase an unlimited internet package from your mobile service provider so that you will not need to worry about the amount of mobile data you use ever again.

You could try what I did in order to find the problem related to the internet calendar.

- Connect an old ethernet hub (not switch) between the AP and the modem. (They might be one product so then you need to find a separate AP or WLAN router for this)
- Connect a PC with Wireshark or other packet capture software to a port on that hub
- Force the iPhone to associate to that AP/WLAN router. Mobile data turned off
- Capture all packets for a long time. Remember promiscuos mode in Wireshark
- Find the sessions consuming data with statistics/conversations. Sort on bytes

Might help with a little networking experience in order to analyze some of the details from this capture.

Well with that Onavo app you could check to see which apps are using the most data & better manage as a result. Check through it to see.