If you added the sim on and there were no discounts for taking it then you won't lose the discounts active in your account, however I unfortunately have no way of checking so you'd best be calling in to 0345 45 1111 and going through options 1,1,4,4, and someone from retentions will be able to take a closer look.

** I work for VirginMedia but all opinions posted here are my own.