Yes, if you force the phone to WCDMA, there's no VoLTE. My only suspicion is some kind of carrier profile on the phone that is preventing 3G calling.
Do you know the current CSC for your phone? The reason I asked where you got it is to rule that out. I know some US operators will cripple features if you use a different SIM. To fix it you need to change the CSC. It's possible on some Samsung phones, but you might have to remove the SIM to do it.
Find your IMEI first. Dial *#06# to find it, or look for a label on the original box.
Dial *#272#IMEI# to change CSC (may not work on all phones). Backup your files because this will factory reset your device.
@z10user4 I'm not too concerned with the other settings in that menu. DSDS is for dual SIM capability.
You can find the CSC in Settings/About phone/Software information - Service provider SW ver.
The IMEI is near the top of that Radio Switcher screen. Right of you to not include it here.
That dial code didn't work on my A31. Although now sheytoon has gone and made me want to try it with the SIM's out 🙂 Soon.
@kb_mv I haven't but this is the only s8 I've dealt with.
@z10user4 Here's the rest of the info. Also I found an old inactive telus sim in a box of phone stuff. Obv I can't use it to test, but when I put it in the phone the option for VoLTE popped up in the connection settings on the phone, so I can now confirm that the VoLTE setting is indeed set to off even if it's hidden with the PM sim in 😛
@Thom20 try going back to nougat. check to see if the sim works right away don't restore your apps etc.
@gpixel4 The link to Nougat 7.0 firmware is broken, I could only find a working link for 8.0 instead so fingers crossed. Anything older than that asked for a paid sub to download.
I'll keep you posted.
@gpixel4 Hmm, I can't get the old firmware to install. Odin just fails every time I try it. I'm getting this error on the phone "sw rev check fail : [abl]fused 8 > binary 5"
@Thom20 is your bootloader unlocked? or does Odin do that automatically for you?
look through the xda threads. I'm sure you'll find something there to help you flash
@Thom20 do you know which CSC is active on your phone?
I'm pretty much out of ideas.