Depleting WiFi Data 85GB in 4 months!!!

Purchased a 100GB data bundle on 21 January 2015. To date I have below 15GB left. That is depleting quicker than lightning!<br> I utilise the WiFi bundle for:<br> Check emails daily. Download numerous Word documents for review which are emailed to recipients. Check latest sports scores and results. Read the latest news. View UTube for approximately 5 minutes once per week. Search the net information specific to my discipline. <br> I have an iPhone and use Windows 8.1. My wife uses a Sony Experia C3. All background data is restricted on the 3 devices. I mention this because that is the same response I receive each time from the CellC 'technical service' - those devices are using up the data! I have an iPhone 6 with a monthly 1.5GB day. I use the data for almost the same reasons and yet I cannot complete the amount in a month! NO movies, series or any have ever been downloaded - I do not know how!<br> <br> Please assist because this boarders on the absolute ridiculous. All IT specialists agree that it i impossible to use this amount of data.<br> <br> Warm regards K<br>