Acejavelin,
What version of software are you on?
I was under the understanding that Category A are for Inter-Tel Protocol [ITP] phones and Category D are for MiNet phones, but I seem to recall that there was some crossover at certain versions; although I didn't think it was between A and D licenses.
If I had to make a guess I would say that the 8662 phones would not take a Category D, but that is wholly a guess on my part as I never had Category A and D licenses on the same system before.
Sorry,
TE