I definitely agree that you are better off not trying to sell it to this company. There appeared to be no international trademark on Quolum, however could be a national one, or some combination of words. And I don't really see the reason for them to buy, there is no indication for any volume search for ''qulum''. Rather than buying, they will be pissed off...
However I wouldn't delete it. Try to go your own way with it, offer it to brandable platforms - BB and SQ, and see what happens. It could make a good brandable, and at the end there are thousands of similar companies' names, I wouldn't worry about it.
In the future, never buy variants of names with a single purpose to sell it to one company (I am not sure it was your case, but just saying).