Can I freely switch back and forth between grandfathered plans?

Any change to any other package results in the loss of your grandfathered plan, period. Add-ons/premiums are exceptions.

Can you clarify, please?  Switching from one grandfathered plan (Go Big) to another grandfathered plan (Just Right or Live a Little) means that I'll never be able to switch back to Go Big???

What about the grandfathered discount?  If I switch from Go Big to say, Just Right, will I still keep my grandfathered discount?

Thanks.

Simple, you are locked into the current grandfathered plan you have, period. Any plan change results in lost of your current plan and discount associated with the plan.

You can switch to those plans anyway because they do not exist.

I mentioned in my OP that I do have the ability to switch to a different grandfathered plan, so for me, it appears these plans do exist.  When I go into my account, my current tv package shows as Go Big along with its list (non-discounted) price.  Below that are the various grandfathered plans like Just Right and Live a Little with their list prices and a blue "switch" button for each .  The issue is that only the non-discounted price is listed so two things remain unclear:

1.  If I switch to one of these available grandfathered plans, will I pay the listed price or continue to get the grandfathered discounted rate?

2.  If I switch to one of these available grandfathered plans, can I switch back to Go Big at a later date at the grandfathered discounted rate?

Again, all of these grandfathered plans are showing as available to switch to in my account.

Never heard of anyone having the option to move around in grandfathered packages, since they no longer exist. No option for me on my account, in fact, I have this banner at the top of my account:

"Your AT&T TV NOW subscription is now part of DIRECTV STREAM. Your original plan has not changed but is not available for new sign ups. If you choose to cancel your existing service the original AT&T TV NOW plan will not be available when re-subscribing."

Proceed at your risk!

They certainly offered that option at one point, but that was still under AT&T.  I would normally suggest you contact Customer Service and ask, but I seriously doubt they would know, and if you got an answer, I don't think I'd trust it.  You might try contacting Loyalty and see if they can give you an answer.  FWIW, the only option they appear to be offering me is Live a Little, for more than Go Big.

I stand corrected on my last comment - if I go to the DirecTV site on a mobile device, I'm only offered Live a Little as a "switch" option.  But if I use a browser on a PC, I see all of the old grandfathered plans as options: Live a Little, Just Right, Gotta Have It, PLUS, MAX, and Todo y Mas.  All show "list" prices (with Gotta Have It showing the same list price as Go Big).  Since they are offering that option, I'd think it wouldn't be a one-shot thing, but that you could switch as desired.  However, logic doesn't always apply here, and I wouldn't depend on my thoughts on the matter.  Whether your discount would follow you is a bigger question  - they may well take your discount away when switching to another grandfathered plan, and if they do, they almost certainly wouldn't give it back to you if you switch back to Go Big.  So again, I think you'd need to get definitive answers from Customer Service.  Since I doubt seriously that the level 1 reps you would get on the phone would know (and my past experience is they tend to give answers that they think will make the customer happy rather than trying to find out the actual answer), you'd really need to get the question escalated, probably to Loyalty (or whatever DirecTV calls the equivalent level of Customer Service reps).

I see no options to change either way via mobile or website. Why so many variations between subscribers is very confusing. The only comment noted on my account is:

"Your AT&T TV NOW subscription is now part of DIRECTV STREAM. Your original plan has not changed but is not available for new sign ups. If you choose to cancel your existing service the original AT&T TV NOW plan will not be available when re-subscribing."

I have no plans to change, so it's not an issue.