When did you buy the single licences?
UCC was introduced in early 2015(I think?).
If you bought your licences prior to that, then they've upgraded you. As you have MiCollab, the UCC licensing should work better for you.
I can't know for sure, but when you mention "16 licences", that doesn't sound like UCC licences, it sounds like the Standard licences you get included with the controller. They are useful for IP devices, rather than users.
When your provider adds a UCC licence to your licensing record, that gives you 2 things:
- a licence on the MiCollab for a UCC user + a NuPoint mailbox
- a licence on the MCD, for an MDUG user
(your 16 standard MCD licences can be used for non-MDUG extensions on top of that).
Your provider is likely just as confused as you are. It is confusing, and they keep changing it.