New carrier unlocked GSM M8

[theandies]

The "cingular" APN works, as I believe you found it did. It's just old. It does reference "Cingular" and AT&T hasn't been called that in how many years (10 years, I just looked it up)? And I wasn't sure if the "cingular" APN supports LTE, as I remember folks having trouble with LTE using old AT&T SIM cards and the old APN. But you said you got LTE using this SIM and APN on your old phone, so I'm probably not 100% right there.

The "nextgenphone" APN won't work on old SIM cards. But it will on a newer SIM.

It works. The only problem I'm having now is mms messages. I tried to send a picture and keep getting the "failed to send message after multiple attempts" notification. I've tried all the APN's that I've posted and none of them work sending mms's with LeeDroid.
I just entered the cingular APN and tried to resend the mms but this time I got the notification "generic network failure"
I'll keep messing with it and I think it's time to go to the AT&T store as much as I hate going there. It takes so long to get anything done but if I want to get a new SIM today that's the only way.........damn.

Good thing LeeDroid fixed my battery drain issue so it was the stock, bloated AT&T ROM.