1GB data taken a day before contract upgrade

I loaded 1 Gb of data onto my phone on Saturday around 20:00 at night. Today, the entire gig of data has been taken. My previous contract was a 3gb data contract, I upgraded my package to a uChoose contract for the upgrade. The upgrade is only effective from 1 September 2015, today is 31 August 2015. Now my data is gone even though I am technically still on my old contract. This is very unfair, as my data contract is still active until midnight where my top-up contract takes effect. My phone is now useless as I don't have data or the airtime that comes with the top-up contract, all my balances are 0. This is truly shocking, I tried calling customer care and got placed on hold for almost 10 minutes - which is no help either. the online chat says call customer care, you call customer care and you get placed on hold. So I am *****ed no matter which way you look at it. 1 GB of data costs a lot of money, and for it to be just taken before your contract upgrade date is ****************.