In case you want to rent an apartment in Luxembourg via a real estate agency, please avoid ISK agency. I have had many problems with them for a studio I rented almost a year ago. the problems are still not solved.
they will make you pay for the real estate agency fee (1 month rent +charges ) and they will vanish before you may even get the keys of the apartment.
I was told all real estate agencies in Luxembourg are like sharks, but this one is really like a gost.
I can´t tell you which one is more suitable for a good customer service, but definitely not this one.