Excess Data Usage - 10GB gone in 3 days

I spend about R1500 to R2000 a month on data and over the last year have NEVER used all my Data, until now. Top up on the 28th August 2015, my balance shows I have 10GB and on the 1st September 2015 I have 0GB. I get told it expired, what all of it even that I had put on 3 days before - not likely! I am in a pay as you go deal as I am out of the country for at least 2 weeks a month and I use other sims in those countries. I never buy data on special, offers free data as I just want data to do my job. The so called Manager I spoke to was rude, arrogant, and just very uncaring! Got told to read the small print before you buy, was told it was my own fault and so what did I expect her to do...