If you mean different last names as your travel partner, I don’t understand why you having different last names would matter? Doesn’t each person have their own visa?
It sounds like you were just being shaken down. It didn’t matter what your name was, they just picked something bullshit to shake you down with.
It's not precisely stated in the GP, but most probably that one. Background: Russian and Belarusian spelling of names are slightly different, the latter being orthographically closer to the phonetic value. (The current Belarusian president-for-life is globally known as "Alexander Lukashenko", which is a transliteration from Russian; the Belarusian spelling, again transliterated, is "Alyaksandar Lukashenka". For the originals, see his Wikipedia page.)
N.B. I'm writing this as a non-expert in either of the languages, but I can read Russian.