I beleive the 'clean up' process to recycle the numbers has been tightened up recently so you may find the 021 # you have has been reallocated to a new customer (or is sitting on a new SIM pack in a store somewhere to be sold).

Also, slight OT, but the new plan 'Supa Prepay' has a credit validity period of 90 days rather than 365. This is the default plan associated with Prepay connections packs now, if you buy a new one this is the plan it will be on.