I bought Verizon pre-paid cell phone in March 2004 and had it re-activated in August 2004 with no problems. Both, the initial purchase and re-activation were done in Verizon location in MegaCentro on Carretera Mella in Santo Domingo; I had my original purchase receipt with me, when I went to ask for re-activation.
I do not recall paying extra for re-activation, other then I was asked to purchase relatively large amount of minutes (500 peso or so), but again I may not remember by now. In any case, if there was any re-activation cost then it was very modest.