Did you check Ter review section? Theres fairly recent reviews of girls in Seoul. One particular agency has a fair amount and the girls are avg to abovw avg. or if want english speaker everyone hits up that indy Sarah miehn.
Heres some info on whats available from hi price to low.(One thing. Korea firewalls web searches related to sex. So you will need a VPN access to if want to use the web in korea. But youtube is available. Room salon owners are sneaky so will post there as a video. Just type 'gangnam anma or room salon' in korea or sometimes english. Whatever comes up make sure to just contact the ones addressed in Gangnam.
-Room salons. Best bets ask a taxi driver or some bartender at a bar. Or if want to walk it head toward gangnam,seollung, or Yeaksam startion areas those where all the top room salons are sometimes when your walking you will see business card on the street. Or the youtube. Gangnam room salons are all pretty much the same.
-incall apts. they call it offictels. These you pretty much need VPN. Need to call ahead. If cant speak or read korean your chance low.
-anma bath houses. Just head to Gangnma station and walk. You will see a few. Will say Anma im korea or english. All same service. Avg to good.
-karokke places. All over. Just make sure you want a Doumi/companion girl with 2nd service if the karaoke says none ir no clue what your talking about then place is legit. Get out of there.
-red light districts And bj and hj massage places and backpages. Too many hit and misses. Not worth it so im not going to bother. If really want to try one then head to the other sites.
Last thing. They have literally no references checks. Just call get appt and bang away^^