Regarding my Galaxy S9 SM-G960U1...., I am experiencing an anomaly using Visible Wireless only. The anomaly does not exhibit itself using a Verizon or T-Mobile SIM card.
With the Visible SIM & Wi-Fi Calling enabled but Wi-Fi off, voice service will not work 'somtimes', even though LTE Mobile data continues to work.
The status bar shows 4G LTE and, to the right, an O with a / thru it.
If I try to make a call a message says the voice network is not available.
This hasn't happened with Wi-Fi calling disabled.
Sorry for the issue you are having and we hope this gets resolved for you soon, I had Visible and I had it on a couple differnet phones in the past. I had to contact them through their chat and have them put my IMEI in the system. I was not sure why but they were able to get me going once they did that. It wasn't like it was with some other carriers were I just put my sim in and it worked. They even tell you on there sight that you may need ot check to see if they support your device. They told me they officially support what they sell but your phone may work still.
Hope this helps