Sudden upsurge of Data usage this month— why???

[Shubhra_1359793]

I have had a smarty accident for about 2 years and managed most months with my 8GB data limit for my regular use. But this month (4Nov to 3Dec) my data ran out within a week and I have had to add on 2GB three times !! Annoyed and perplexed as to why?  Any ideas/ suggestions?? how can I end up using 7GB in one evening? 
no, I don’t stream movies etc in my phone 

thanks in adv guys. 

[SmartyTrousers]

Your phone should be able to show you a breakdown of how much data different apps and activities have been using.

[MSF]

@Shubhra_1359793 As @SmartyTrousers advises, look at your phone settings as it will show what app has used data.