Messages App defaulting to sending SMS over WiFi

[Android Central Question]

I have a Pixel 2 XL, using the Google Messages app. Usually, regardless of whether I'm connected to WiFi or 4G, it will send messages, gifs, stickers etc to others using the Messages app without an issue.

A few days ago, I noticed that when I'm connected to my home or work WiFi, all of my messages now default to being sent through SMS (indicated by the word 'SMS' under the 'send' arrow' in the message box). As soon as I switch my WiFi off - the SMS word disappears, and I can send messages over the internet as before. I'll sometimes receive a flurry of messages that were sent by others.

All other internet functions work perfectly fine on the phone when connected to WiFi - internet speeds (60mb) not an issue.

This happens with both my work and home networks, so don't believe it's a firewall issue. Any ideas what could be the issue?

 

[Rukbat]

Check your wifi settings - don't prioritize wifi for phone calls. You most likely have it set to prioritize wifi, which is why SMS (which is a text phone call) is goi8ng via wifi. (The other option isn't internet, as you said, it's POTS - the Plain Old Telephone System - and most text apps can't use wifi yet. That's part of RCS, which is where we're all headed in about a year or two. Then Apple can keep their iMessage protocol as something outdated, not as something that makes SMS look outdated.)