Multiple radio button groups in MVC 4 Razor

Question

I need to have multiple radio button groups in my form like this:

I know it's simply done by specifying the same "name" html attribute for each group.
HOWEVER
MVC doesn't let you specify your own name attribute when using html helper like this:

@Html.RadioButtonFor(i => item.id, item.SelectedID, new { Name = item.OptServiceCatId })  

Because it looks at each tag's "name" attribute (not "id") to map/bind the form to the model which the controller receives, etc.

Some said that specifying each with the same "GroupName" attribute will solve the problem, but it didn't work either.

So, is there any way which works ?

EDIT:
Here's my view (simplified):

@model Service_Provider.ViewModels.SelectOptServicesForSubServiceViewModel

@foreach (var cat in Model.OptServices)
{
  //A piece of code & html here
  @foreach (var item in cat.OptItems.Where(i => i.MultiSelect == false))
  {
     @Html.RadioButtonFor(i => item.id, item.SelectedID, new { GroupName = item.OptServiceCatId })
<br />
  }    
}

NOTE:
My model is a List<OptServices>:

public List<OptServices> Cats {get; set;}

And OptServices has a List of OptItems inside:

public class OptServices
{
//a few things
public List<OptItems> Items {get; set;}
}

Answer 1

all you need is to tie the group to a different item in your model

@Html.RadioButtonFor(x => x.Field1, "Milk")
@Html.RadioButtonFor(x => x.Field1, "Butter")

@Html.RadioButtonFor(x => x.Field2, "Water")
@Html.RadioButtonFor(x => x.Field2, "Beer")