I've seen UTC and OTC used what does it mean?
OTC usually means "outside the club", as in "dating" a stripper to get the "extras" but to do so in a motel, hotel, or (much less commonly) her place or your place.
Its opposite is obviously ITC, or inside the club.
I've also seen UTR, which is "under the radar", referring to a provider who wants to keep a very low profile, avoiding advertising and other publicity of all sorts.
As to UTC, I've never seen it. Are you sure you didn't really see ITC or UTR? If it really was UTC, show us an example.