WiFi Calling

Only the word "Wi-Fi" should appear. Regardless, if it does and this issue persists, then the problem may be with your local wireless network. Specifically with the available wireless bandwidth that your iPhone is connected with.

If you don't believe that your wireless network is the issue, then I suggest that you contact Apple Support directly for further assistance with this matter. To do so, simply select the "Get Support" link in the upper right-hand side of this forum's web page.

Just to be sure, if Wi-Fi Calling is available, you’ll see Wi-Fi after your carrier name in the status bar. Is this correct in your case?

Ref: Make a call with Wi-Fi Calling - Apple Support