Since it is a ccTLD, it is a nepalese internal matter and I don't see why ICANN should be involved at all. Ask local authorities, write to the governement, raise the issue in the local Internet community, etc.
If Mercantile are also registrars for gTLDs as well then you talk to the Registrar Compliance Program staff and see if they can nudge them. There is a form that you can use on this page to register complaints about ccTLD registrars; http://www.icann.org/en/resources/compliance/complaints
Another point to consider is that the policy of having to show up in person may be a policy dictated by the government and/or the registry, not necessarily the SRS provider or the registrar.