It's been a while I am trying to call Nepal and got couple different calling cards and most of them ended going to ZERO value but couple times I was able to connect small town but not Kathmandu.
I think it has something to do with the NTC, which is blocking most calling card calls and we seeing these problems. It is not only Himtal card has problems but rest other calling cards facing the same problem.

This is my personal opinion as I am having trouble to call Kathmandu.