While these big businesses should be punished for their misdeeds, many businesses I have dealt with in Nepal don't really pay much of a consideration to billing - things get cheaper if you do not get a bill. 

Also, why only boycott Wai Wai? If you really want to go that route, why not boycott everything from the tax evaders (which I don't think would be realistic)?

It is interesting to see how this story is unfolding. There's this list of big businesses involved in this act of fake bills (which seem to be include all of the big businesses of Nepal) and then all of the blame seems to be heaped onto Wai Wai and the Chaudhary Group. 

I guess a punishment according to the current standards would be a good lesson for all for the future. Boycotting Wai Wai would basically mean that more people would need to go to the Gulf and Afghanistan for work.