Yes you can this is no problem at all, although they might tell you otherwise. As an example if you look at the "new" EFTA B permits they are valid for 5 years. If you were already here 3 years when it was issued then you are able to "upgrade" to a C permit on application after owning the B permit for only 2 of the 5 years. I dare so loads of people on the forum have done this. The same applies for an L permit where you can also apply to have it upgraded on the grounds that it was wrongly issued and should have been a B anyway. If you are the owner of a Swiss registered incorporated company(i.e. AG or SA) you have the right to apply for a C permit from day 1.