Closest answer I found on the internet was this:

So, things not working says that you might be configured for the wrong network, and the phone is eating battery trying to find whatever network it is searching for.

This is very rudimentary, as many internet searches are, but it suggests that you get help in proper activation, whatever that means. Someone would have to have a good understanding of your phone and the carrier.

Good luck.
My ex's battery on an old phone was tanking at work. She put it in a locker and it was wasting battery searching for any signal (that's the hint, searching for a signal/network) and the solution (not yours) was to put it in airplane mode when locked up behind metal. (the old tinfoil situation)

searching to connect the phone and text message apps and it couldn't (though baffling that web-browsing worked perfectly fine). I'm also thinking (or hoping) ConsumerCellular's help is likely to be better on this issue than it was back in October when I first had the problem with the new SIM card, and they have more experience with the difficult cases. So we shall see.

I'd hate to be wrong -- my phone would be pretty close to worthless if the battery life is cut to 1/3. $850.

Just a wild guess. I don't even know if you have wi-fi, but I would sometimes find my phone connecting to xfinity wifi, via an account I have there.

xfinity lets people all over the place share their hotspots with other xfinity account holders.

Owners of the wifi units can opt out, and their hone network is isolated.

Apple will route calls and messages over wi-fi (don't ask me the details). I don't know about others.

During the time I had the NEW Sim card in, I never took it outside (I was sick and mostly bed-ridden). So during the whole time I operated in the usual at-home mode.

For me, that means Wi-fi on the phone is turned on (and close to the computer modem that is the source of the Wifi around here) and Mobile Data (meaning, in my jargon "over the air" from cell-towers) is turned off.

So during this period, I never tested it away from Wi-fi.

At least not per my recollection. I could be wrong, but the above is probably right.

So yes, I'd have been curious how things would have worked away from Wi-fi and with Mobile Data on.

My normal procedure as far as cellphone settings: In the house: Wi-fi on and Moble Data off.

Away from home: Wi-fi off and Mobile Data on.

CC claims to use the strongest network that they use in each area that they cover. Do you have as many bars with the new sim card as with the old? If you do, the problem is probably with your phone.

within 4 feet of the modem that is the source of the Wi-fi. I don't think I experimented with Wi-fi off (and Mobile Data on), if I did, the phone behaved the same way.

Right now, with the old SIM card in the phone (as it's been since October after re-replacing the new with the old card) I have 2 bars (out of 5), but I'm also connected to Wifi (I don't think the bars are significant if I'm connected to Wi-fi). If I turn Wifi off on my phone and turn on Mobile Data, the Wifi symbol on my phone goes away, and a "LTE" shows up. I still have 2 bars.

I have been away from home lately many times and walking several miles operating on Mobile Data on and Wi-fi off (again with the old SIM card, and including recently) and everything is fine.

I have no experience with the NEW card away from Wi-fi, I don't think. I can't tell you how many bars it had with the new SIM card, I'm sure I looked at it, but I can't guarantee that I did. But as I said with previous replies, Internet browsing went just fine with the new card, whereas trying to text message or use my phone app gave me some error message about the network, and it wasn't a message about signal strength. i just can't find my notes from last October where I wrote down the error messages.

As for CC switching the network, I don't think so, not yet. My phone works just the same way as it did years ago, last year before the period where I had the new SIM card in briefly (a few weeks), and since October when I had the old card back in. In all these old SIM card periods, I never had problems with any aspect of my phone due to low signal strength or incompatible network or any of that.

But for sure CC wants me and other obstinant troglodytes to switch to their new network. With the new SIM card, and it being properly activated, that's what will happen as I understand things.

Thanks much for reading all this and for replying above.

Signal (Verizon) would often go to zero.

I gave up and signed up for DSL, which is actually much better. Phone took its chances with cellular away from home. In the foothills, signal was in and out.

Neighbor said he was switching from DSL to cellular internet, 5G. I freaked, cuz the 4G was a joke much of the time.

I switched to spectrum. Same Verizon network. But when I replaced the very old phone with a new one, it picked up 5G, which has been solid by comparison.

Maybe the 4G transmitter was behind a tree and the 5G is on a fire watch tower I can see clearly.

Keeping the DSL. My objection was and is that I pay for landline phone that I don't use, but phone+internet is cheaper than internet alone.

Life is sometimes sick and twisted, but I will save the money. Never got a landline phone.

My modem that feeds my computer with Internet is plugged into a DSL. My landline (yes I have one and have had for decades) plugs into the modem. The modem also generates the Wi-fi signal that is what my cellphone uses when I'm at home (and I have Wi-fi on my cellphone turned on). My Internet and landline is a bundle deal with CenturyLink. My cellphone is wtih ConsumerCellular.

So it's all a happy family.

But lately I discovered my landline doesn't work and I haven't finished troubleshooting it a little before calling CenturyLink (hate to pay $150-$200 only for them to find out that its a loose connection somewhere or something simple like that on my end, though I have wiggled and unplugged and replugged every connection I THINK. Will have to find and drag out my lovingly-drawn connection diagrams and go over everything.

I had hoped to call ConsumerCellular on my landline so that I could talk on it while fixing whatever needs fixing on my cellphone. But since my landline doesn't work, forget that option.

So, if I still have trouble activating my new SIM card, I'm kind of screwed because I can't use the cellphone as a phone or a text messenger until I've activated, sigh. But I'm sure that ConsumerCellular has many customers that are one cellphone only. And there's always Chat on the computer.

If you're curious, I keep my landline because I was making some long distance calls to my farmer/leaser and my extended family 2,000 miles away, and the voice quality of the cellphone was just not as good as the landline, and problematical. That was years ago and I don't think a problem lately, but if the landline isn't costing extra, I do love having two lines and two modes of phone communication.

Apple stuff routes everything everywhere. Watch, too. It's a little weird. Like Dick Tracy.

Phone prob once was just a loose connection. Decades ago.

Telco charges for "long distance" so I only use the cellphone to call. I forgot the number.

Good luck.

Like you, I've changed sims with ease any number of times in the past, but couldn't get this one to work. CC sent me to a retailer to have it done, but it was in a ritzy part of town and the only parking was $20 per hour. Went home, called CC and they sent me to another retailer who couldn't figure out how to connect.

At this point, I'm thinking about just getting another phone.

It's disappointing because this is the first time (after 10 (?) years) I've had a complaint about CC.

it would work this time. I was hopeful that CC help would be up to speed on dealing with the more difficult cases than last October when I last tried, and that CC instructions would have improved. But reading your post makes me worried again. I sure wouldn't want to have to get a new phone as that is very time-consuming (for me) as well as $ costly, and my current phone is fine except for the SIM card issue.