Often in the same call center 2 supervisors will tell a different answer on the same matter...
I don't see why a client would loose a HD grandfathered package because he changes his SD themes. If, for example you want to change VARIETY 1, let's say for SPORTS 3, all the agent has to do is to open a work order, press - netx to the VARIETY 1, then go in the upper part of her screen, go in the middle box, find SPORTS 3, click enter to be able to select and confirm.
The codes of the old HD package are probably no longer in the system, meanning that if you choose to go with the new package and then call back and say you want to go back to the old one they won't be able to do that, or if you have a retention offer of a % off each month for a period, but in that situation it shoudn't change anything.
I suspect that some agents, when they know their RPC (revenu per call) is low for the month and a client with a HD granfathered package call to make a change that won't change anything for them (like swap 2 themes) tells the client that it would change the HD package and they go ahead and change it to have an upgrade of 5$ (cause they select the 5 themes)