Discovery Covid vaccination registration is pointless

I received an SMS with a voucher for a Covid vaccination today, but the location is over 30km away. I phoned Discovery, went through to the Covid line, and told them what had happened, and asked for a closer venue. I was told that as I had the voucher I could not go to an alternate location. So I commented that if I didn't have a voucher, could I ask Discovery for a location and was told - no, I have to have a voucher to have a vaccination, but then of course I can't ask Discovery for an alternate location. So - what is the purpose of registering on Discovery's Covid page, it's pointless.