SfD charge clarification PLEASE HELP

My last game I tried the ynnari rules with my dark eldar army.

I managed to kill a unit with some reaver bikes on the charge, I trigger SfD.
They're no longer in combat, I declare a second charge. I make the charge to a marine squad close by. I then start to resolve attacks but my opponent gets really salty saying that can't be right and a few people start looking up the rules.

Now to me, it's clear, you charge and thus you fight ( you can't usually fight twice but SfD allows it - the same as the choice of shooting twice).
The second choice of SfD - attacking in combat is there incase I'm still locked in combat so I can choose to fight without charging a unit.

My opponents (I should say friends, they're not being funny it's just a genuine difference of opinion)
Say that I can charge but not fight, because it's a different step, it lets me charge into a different unit but I can't attack. We agree that if I was locked in combat and used the other combat choice,, I could attack a second time.

So to me it's clear as day, you charge, you attack. You don't charge and stand there being hit it sounds silly. But all the rest of the group agree on this and I want the internets opinion.

I gratefully welcome any feedback

I am afraid they were right SfD allows you to either charge or fight. They are listed as two separate actions for SfD. The point of the charge is to lock another unit in combat.
EDIT: if it is too far for consolidation.

A bonus charge does not allow you to fight a second time for free.

In (each) assault phase, every unit you have locked in combat may fight once. SfD can be used to allow them to do so again. Alternately, it can be used to allow an immediate charge. If you use SfD to perform a charge during the assault phase, with a unit that has not yet fought, then you can still activate them to fight once.

Ok then, fair enough.

At least I get a second chance at a failed charge!

Thanks for clearing that up guys.

When you do "fight" its treated as a "fight phase" go you follow those rules that man people forget about 1 very important rule the number 2 rule.

Pg 182
5. FIGHT PHASE
1. Choose unit to fight with
2. Pile in up to 3"

So if you are within 4" of a unit you can SFD to fight that unit. Doesnt sound like much but its easy to get within 4" of a unit and Soulburst.