you need to ask the Korg you want to use as a reference.
If they vouched for another Monger, also MO, that doesn't mean they will do it for you or that they do it anymore.

I've asked orgs i've used and all say they do not share references. Many did in the past.

Some will give a ref for one org but not another. It's trial and error. I even had one org that exchanged with a Latin-Brazilian service.

It's strictly a business relationship, so their willingness to take the time to give you a reference is directly related to what kind of a customer you are.  If you are low volume or an infrequent visitor, what motivation do they have to help you out?  

 
When I have been asked to mentor new members in the Kgirl scene, I always ask them what they expect their frequency to look like.  If you are a once or twice a month, then it's more effective if you concentrate your first several months at one agency and build your value as a customer.  As you increase your volume, as many do that get hooked on Kgirls, start expanding to different agencies.  frequent customers will seldom get turned down for a reference from a booker they have done a lot of business with.  

 
Too many newbies get impatient and want to see the top girls at EVERY agency when they have no track record a booker can look to for what kind of reference he/she should give, if any at all. Frequency, respectfulness, tipping and how the girls have reported back about you are all considerations in getting a reference.  Some may have a different opinion, but this is how the guys I have helped approached the business and all were successful, . . . .except one, who was a little rough with the girls even though I warned him against it.  He's BL'd now, just about everywhere.