Sanral parking lot query

I have been a Sanral E-tag holder for a number of years now. I learned along the way that Sanral E-tag holders would be parking for free at particular malls, with their payments deducted from their accounts. I don't remember ever seeing any parking lot branded as a partner to Sanral nor what e-taggers should do at such parking lots. On 16 July I drove into Centurion Mall around 11:00. I collected a parking card from the machine and got into the mall. A while later I saw an sms of Sanral welcoming me to the mall. Only that. In the afternoon I went to pay for my parking, which cost R10 and as I left, another Sanral message thanked me for using the Centurion mall. On getting home I realised another R10 was deducted from my Sanral account. Is this normal Sanral, that I pay twice for using parking lots in your network? Why is there no branding to warn tag holders of what is expected from them? I presume the R10 debited from my account will be reversed as I had already made a cash payment.