That is a rep dependent thing but some of them freak out if you have a data only device on a phone line. Verizon cannot stop you from doing this but the reps are not lawyers and are capable of taking away your UDP. So don't call with a tablet on a phone line and of course stay away from corporate stores except to just go in and look at devices, but don't let them look at your account.
----------
What MHS device do you use?
----------
Well if it were just up to Verizon, they would not allow you to do that. The issue is that because of the terms of the Block C licenses, Verizon cannot stop you from putting your SIM card in any compatible device.
Again, the reps aren't lawyers and it is a YMMV kind of thing with the reps. Don't let them see a data only device on a line with voice minutes. End of problem.