[LocMax]

on top of script: new bool:Refunded[MAX_PLAYERS];

OnDialogResponse > register part: Refunded[playerid] = false;
OnDialogResponse > login part: Refunded[playerid] = true;

OnPlayerSpawn

if(Refunded[playerid] == false)
{
// give rewards here..
Refunded[playerid] = true;
}