Beginner need help with C# assignment

Question

Scenario:

You have been tasked by a telecommunication company to develop a payment

system. This system is part of a bigger one. Although the company has many

payment models, for the purposes of this project, we shall be limited to only the

following entities:-

(i) Fixed Line Services

(ii) Mobile Services

The company has subscribers which it keeps track of, so that it knows what bills to generate at the end of a billing cycle. Fixed Line Services form part of the subscribers. This service consists of a fixed line rental and a call chargedepending on how much the service is used. Mobile service consists of a callcharge and optional SMS and 3G charges.Your system shall be a console based program. It shall offer the user, the abilityto input in details of fixed and mobile services. Lastly, it shall have to ability tocalculate the total bill payment of the fixed and mobile services in the system.

It is expected that you will be using object oriented features and concepts such as

Classes, Objects, Inheritance, etc.

so far i have done this: (i get the idea of how the basic structure should look like but i am lost on  how to implement and store data in the classes)

using System;

using System.Collections.Generic;

using System.Text;

public abstract class telephonysystem

{

class Telephony

{

string subscribername;

string ServiceType;

decimal CallCharges;

public string getName()

{

return subscribername;

}

public void setName()

{

subscribername = sn;

}

public string getService()

{

return ServiceType;

}

public void setService()

{

ServiceType = st;

}

public decimal getCharges()

{

return CallCharges;

}

public void setCharges()

{

CallCharges = cc;

}

}

class MoblieService:Telephony

{

decimal FixedLineRental;

public decimal getLine()

{

return FixedLineRental;

}

public void setLine()

{

FixedLineRental=flr;

}

}

class FixedlineService:Telephony

{

decimal smsCharges;

decimal threeGCharges;

public decimal getSms()

{

return smsCharges;

}

public void setSms()

{

smsCharges = sc;

}

public decimal get3g()

{

return threeGCharges;

}

public void set3g()

{

threeGCharges=tgc;

}

}

}

namespace Telephony

{

class Program

{

static void Main(string[] args)

{

int line;

Console.WriteLine("1.Fixed Line accounts");

Console.WriteLine("2.Mobile Line accounts");

Console.WriteLine("3.Exit");

Console.WriteLine("Please select a line type: ");

switch (line)

{

case 1:

break;

case 2:

break;

}

 

 

}

}

}