Windows phone using too much data

[nickismyname]

i have a fairly small data package each month, but i can easily get by just using wifi and only using whatsapp when i go out, but with my wp i seem to use a huge amount of data.
Each month i get 100mb free, and this used to suffice because i would only use whatsapp and use my phones other connection capabilities when i was connected to wifi, but now i suddenly use 10mb randomly on answering 2 or 3 whatsapp messages, if any knows why i am using so much data so quickly please tell me and how i can prevent it.

 

[miki20021]

Mind that if you take pictures with your phone, WP has an automatic-upload to sky-drive.
Check if you blocked it.

 

[instantcoffe]

Also, check what other apps might be using your data (every app nowadays is updating constantly - on my HTC 8S I have Skype, Facebook,and TuneIn Radio that are running in the background - with no way to stop them except by blocking my data).