SIM card hell - New SIM card required by Consumer Cellular, but it reduced battery life down by 2/3

[progree]

They are increasing the pressure on me to install the new SIM card by increasing the legacy network charge from $5 to $10/month if I don't...

My phone is a Galaxy S10e (Android), purchased new in late 2019.

Last August, Consumer Cellular (CC) said my SIM card was obsolete and I promptly ordered a new one. But I couldn't figure out how to install it (and yes I've put in SIM cards before in other phones without problems).

To make the long story short, I finally, after searching for videos, found a way to install it - see [1] below. But my phone app and text messaging did not work at all, and the battery life was cut short from 3 to 4 days to 1.3 days if not used at all, to something much less if I used it (for web browsing or listening to TuneIn -- like for my typical trip away from home for a few hours it wouldn't have held up even if fully charged at the start). Yes, I have a battery pack but using it would require considerable recharge time and maybe 2 recharges - not practical.

I called CC again and we didn't come up with a solution. So I replaced the new SIM card with the old one and everything was fine, including the battery life which was back to the 3-4 days.

But they've been bombarding me with texts, emails, and phone calls for months about how they were going to charge me a $5/month legacy network surcharge until I replaced my SIM, and that eventually my phone might stop working. (I've been paying the extra $5/month for about 3 months so far). Today they said they would start charging $10/month extra.

One thing when I had the new SIM card in for awhile -- I think the problem on the phone app and text message app not working is that I may NOT have successfully activated it after installation (my notes are confusing about that). But to check this out and try again, I hesitate to try again because I fear once I successfully activate it, I will end up with the too-short battery life, and I won't be able to go back to the old SIM card. So I've just swallowed the $5/month surcharge and kept the old card in. But an extra $10/month is starting to get pricey, and they may just keep increasing it, and like they say, the phone eventually might not work at all.

FINALLY, THE QUESTION: Has anyone had similar difficulties with new SIM cards causing a huge reduction in battery life? Am I right to think that if I install and activate the new SIM card, there's likely no way in hell of being able to use the old SIM card again?

Thanks much in advance

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[1] (Not essential details, no need to read) The instructions sent with the SIM card were horrible and a couple of calls to Consumer Cellular were not helpful. And I broke the little key thing that one pokes in the hole, and they wouldn't send me a new one. Though she said a partly straightened out paper clip would work. I finally found a video that was just exactly like my phone that showed exactly where to poke (the CC written instructions didn't even have that info), but I bent to uselessness a couple of paperclips. Still no dice.
      I finally found a video about dealing with phones whose SIM card drawer didn't pop out (partially) like it should when the hole is poked: Use a LOT of pressure to poke as some old phones' SIM drawers sometimes get stuck. But I had already used enough pressure to bend a couple of paperclips. And other instructions I had encountered warned against applying too much pressure.
      But anyhow, I unbent another paperclip, held the last 3/8-1/4" or so of it with my needle-nose pliars, under the theory that only the most extreme force would cause 1/4" of paperclip to bend. It worked -- I was able to push it in the hole with enough force to pop open the SIM tray.
      I put the new SIM card in (instructions were horrible and it was some kind of thingy where actually it was 3 SIM cards in one, and one had to figure out which one, and its orientation, is the right fit for the phone. It was the smallest tiniest chip of the three. And the online instructions to activate it went all over the place link after link after link, and eventually I think I activated it, but am not at all sure. As I say in the above, the new SIM card didn't work.