Vodacom Data Being Drained/Depleted - Inexplicable

In the last 5 months I bought an LTE router from Vodacom. I need it for email and sending reports to clients. I previously was on a 500MB contract with CellC, that I seldom finished in a month period. In the past few months ALL of my 3GB data has disappeared by the 6th of the month. This is inexplicable. NO - I am not utilising YouTube