24-month 99 top-up with 21-month bis???

I took out a Top-up 99, BIS included contract on the new red blackberry special on 15/05/2011. On 15/02/2013 I upgraded with the idea that I had BIS included until the end of my contract which is 15/05/2015, seeing that my initial and upgrade had BIS included, which to me is 48-months.<br> Now Vodacom tells me that my contract expires 15/05/2015, but my BIS expired/02/2015, because of the early upgrade. I queried this 16/02/2015(082111 Ref: S3-8XO6A-AYM8) whereby they said Vodacom made a mistake and they'll rectify it.<br> Come the 01/03/2015 my BIS has been de-activated.<br> I queried this again 02/03/2015(*** Call ***).<br> Now I have the same fight again and here is my case:<br> Surely if my original 24-month contract which included BIS ran from 15/05/2011 to 15/05/2013 and my upgraded contract which also included BIS ran from 15/02/2013 to 15/02/2015. What happened to the included BIS from 15/02/2013 to 15/05/2013 where the contracts overlapped. How can BIS expire 3 months before actual contract expires when I had 2 24-month contracts, both including BIS? This means that either my whole contract expired 15/02/2015 or my BIS needs to be re-activated to run to 15/05/2015. Christo