public MobileAccount(MobileOperator mobileOperator)
        {
            _operator = mobileOperator;
            _number   = _operator.GiveNumber();
            _operator.AccountRegistration(this);
            _name = "account" + _number;

            Contacts = new List <Contact>();
        }
        public MobileAccount(MobileOperator mobileOperator, int balance, int callPrice, int messagePrice)
        {
            _operator = mobileOperator;
            _number   = _operator.GiveNumber();
            _operator.AccountRegistration(this);
            _name         = "account" + _number;
            Balance       = balance;
            _callPrice    = callPrice;
            _messagePrice = messagePrice;



            Contacts = new List <Contact>();
        }