[De4dpOol]

That won't be so much different. Here is my try...

pawn Code:

CMD:checkphone(playerid, params[])
{
    new pn,string[128],name[MAX_PLAYER_NAME];
    if(sscanf(params, "u",pn)) return SendClientMessage(playerid, -1,"USE /checkphone [Phone Number]");
    for(new i = 0; i < MAX_PLAYERS; i++)
    {
        if(YourPhoneNumVariable[i] == pn)
        {
            GetPlayerName(i, name, sizeof(name));
            format(string,sizeof(string),"Number: | %d | User: | %s |",YourPhoneNumVariable[i], name);
            SendClientMessage(playerid,-1,string); 
        }
    }    
    return 1;
}

Again not sure if it will work.

EDIT: It will not work if you are saving phone numbers as string.