Bad service

I wasn't even interested to call in the call center. I want an explanation as to where the data I had on my phone went to. When I did an upgrade a month ago I saw the device I wanted came with 20GB once off and did not stipulate that this will expire on which date I wake up today expecting to get my R390 airtime and my data which was about 9GB if not 10GB because the last time I checked was on 26 or 27th April that I had 10.2GB and boom I'm now on 900MB that I don't even know came from where. I want that data reinstated with immediate effect or let me know if I should take this further. If the data had an expiry date that should have been stated on your page.