What network does TN really work with now?

Howdy Folks !!
I have a wifi only phone that I use for TN that used to be on their free service too - and it has the $5 (?) number keeping deal on it, but that is all.
It still has the TN SIM - and got an SMS saying that the SIM has been deactivated - no biggie to me as that phone stays home 24/7, but...

Logged into that account & it wants to sell me their .99 SIM kit - checked a couple of IMEIs & nuttin is OK with them, so now I wonder - what is all this & what does TN really want from its free cellular users ??

Thanks for any education !!

TextNow SIMs are now T-Mobile. If your last test with T-Mobile kept yielding good results, the .99 SIM seems well worth it. (They've been $0.99 for a while, always before $5-- I don't know if it's temporary.)

I've heard mixed experiences about whether or not T-Mobile verified VoLTE is required or not. Early reports indicated it was, which seemed ironic since TextNow is exclusively VoIP, and not cellular voice at all. But I've seen other reports that a phone with the right bands will work without VoLTE capability, even if it doesn't clear their IMEI test.

I just tested 2 IMEIs: one for an Asus Zenfone LiveL1, which may or may not have T-Mobile VoLTE, and a pretty old AT&T Prepaid Alcatel Ideal. Both cleared, but I'd guess they both might be pretty marginal for the T-Mobile network.

Hi KentE & Thanks for your reply !!
Always good to hear from you.

Cheap is good & .99 is nifty, but since my wifi-only TN phone works here at home & their checker barfed on both that & my sort of orphaned Truphone AT&T phone...
I should probably consider myself blessed by having such great, cheap, unlimited service from Twigby lately and not worry about getting any more AT&T for myself.

Truly the only aspect of this I find troubling is the forced obsolescence factor - that my former AT&T phone ain't the newest - just an unlocked GSM phone...and now it is not really useful to me for that purpose anymore, sigh.

I probably should have mentioned, for the 2 phones I tested:
The Zenphone is factory unlocked, and the AT&T Prepaid has been unlocked. The tester doesn't take locked status into consideration, but the AT&T Prepaid device wouldn't work if it was still locked.

I went into my app to try to order the SIM and the price is $4.99 for me. However, I haven't paid the $5 cost to lock my number.

This link should take you to SIM offer for general public, showing .99 to me as I post this.

Thanks, Mark-- that link has some extra APN settings for problematic phones that I hadn't seen elsewhere.