Creating correct concrete type from database read

A project I'm working on would benefit from having a little more abstraction added to it and I'm faced with a problem I can't seem to get past.

Essentially is we have services that can be assigned and consumed, but the rates at which they are consumed are all a little different. This distinction is important for reporting and for scheduling the consumption of these services.

I'm not really sure how to take data I receive from the database and ensure that the correct concrete type is created. Am I overthinking this and there is something easier I can do? The only thing I can think of doing is having a switch statement determine which type to make based on the unit of time specified, but that seems sloppy.

UnitInterval (which I'm welcome to renaming it something that seems less confusing), is supposed to hold the service's consumption unit (1, 15, 30, 60) and then the UnitSize will be minutes, hours, or days. The UnitSizes are held in a reference table and ID'ed with their appropriate text of Day, Minute, Hour. So in my table Minute has an ID = 1, Hour = 2, Day = 3, and depending on if these intervals need to be adjusted they can be in the future.

How do I get something like the UnitSize from the database and ensure the correct implementation? Am I just going about this the entirely wrong way?

Essentially my end game is that I'll have another class which just contains List<WorkableService> that I can use to spit out a report with the correct units, any costing, duration, etc.

public abstract class WorkableService
{
    public int UnitSizeId { get; set; }
    public string UnitSizeText { get; set; } 

    public double UnitInterval { get; set; }
    public abstract TimeSpan Duration { get; }
    public double UnitsAvailable { get; set; }
    public double Adjustment { get; set; }
    public decimal Rate { get; set; }
}

public class MinuteService : WorkableService
{
    public override TimeSpan Duration
    {
        get
        { 
            return TimeSpan.FromMinutes(UnitInterval); 
        }
    }
}

public class HourlyService : WorkableService
{
    public override TimeSpan Duration
    {
        get 
        {
            return TimeSpan.FromHours(UnitInterval);        
        }
    }
}

public class DailyService : WorkableService
{
    public override TimeSpan Duration
    {
        get 
        {
            return TimeSpan.FromDays(UnitInterval);
        }
    }
}