We're stuck in a strange situation. We are grandfathered into an unlimited data plan with AT&T but if we upgrade our phone we lose the unlimited data. Our phone is about five years old now so the phone is good for almost none of the things we want to do with the data plan! We just lost another service which is now incompatible with our phone and our phone's manufacture hasn't issued an update for three years. So we wonder if being grandfathered into an unlimited data plan is really worth enough to not upgrade to a newer phone.
We looked into other providers but T-Mobile, Sprint and the rest don't serve all the places we need service, and Verizon is no less expensive than AT&T.
Since when do you lose a grandfathered plan when you upgrade your phone with AT&T? We've been with them years and years, even before they were AT&T and never had that happen. To the best of my knowledge you only lose the grandfathered plan if you change plans. Once you do that, you can't go back. Unless this is a very recent thing?
We kept my DH's unlimited forever and upgraded phones like clockwork every two years. The problem was that he'd get to a certain point and they'd start throttling his data, so then he wouldn't use it. Because he is the main account holder and had unlimited none of us could use mobile hotspot to tether. So here we were paying $30 for unlimited and then $30 apiece for DD and I to have 5GB each and we weren't really using it because it wasn't usable. Then of course you're paying separately for texting, the minutes etc.
When I sat down and really looked at it we were paying all this money to stay in a grandfathered plan that we couldn't really utilize. In Sept I went to a 10GB mobile share plan and because none of us were on contract my bill went WAY down. Unlimited talk and text and 10GB is plenty and a half for three of us. When they were running the double your data plans of 15GBs or more I called them, asked for retention and got them to double my plan to 20GBs for no extra charge. Just had to be firm but nice.

I've since upgraded DD and myself on the Next plan. If and when DH finally caves for an upgrade, my bill will only be $5 more then I was paying for the grandfathered plan we didn't use and I now have a very usable plan. We don't come anywhere near 10GBs let alone 20 plus I can tether now and that's come in handy more than a few times. Oh yeah and this month they are starting to roll over data from one month to the next. It doesn't accumulate like minutes did but you do get leftovers from one month to the next which is nice.
So, if you're not using your unlimited and you keep losing features, what's the point in keeping it? Sit down and really look at your bill, see what you use and compare it to one of newer mobile share plans. For me there was no downside. I have a plan I can actually use now. If you go Next for an upgrade versus a two year contract your bill will be less as well. People misunderstand that plan thinking you never own your phone but that's not true, you pay it off just like you do in a contract then it's yours. Even better, you can pay it off any time you want and it yours.
eta: When I went in to change my plan I made the guy write everything down in detail, in columns-old plan, mobile share plan, share plan with next and share plan with contract. Then I went home and went over the pros and cons for each before I decided.