I already have a smarty sim can I reuse it

You used the Smarty SIM already, and ported your number out ? 

If so, the SIM is effectively dead, so you need another SIM, costing around 99p from newsagents and supermarkets. Amazon recently had an offer on SIM cards, including Smarty, for just 10p each, including free delivery, which may still be available.

EDIT : They are now 15p