MMS and wifi

[Installfraud]

I replied to a previous post about this but would like to start a new thread as I feel like this problem is ongoing and it doesnt seem like there is a fix . I have an unlocked verizon s9 and my wife has an s10 which we purchased from comcast around 900 dollars. A few months ago they both stopped sending pictures while texting. We switched from verizon whith whom I never had this issue. We were both using Samsung's messaging app at first after switch. When we started to have this problem and found out it was not uncommon with Samsung's app so i installed Verizon's message + on both phones and it worked. Pictures would send as usually with wifi and cellular on no problem. In or around December my wife's phone stopped sending pictures again.they would hang on sending in the app Only if wifi was manually switched of would they immediately send. Or if she walked or drove out of range hours later would they send. Then my S9 started doing the same thing . Verizon's app no longer works to send mms when wifi and cellular are both on. Wifi must be off and cellular on . Not a big deal some might say other than an inconvenience. I disagree . Paying 1800 dollars for 2 phones I would think technology would allow something so simple. It matters because my wife who sometimes will forget to turn the wifi back on her phone after she need to send a picture or use an app that's sends mms . Not a big deal if you're on an unlimited plan but when your on a shared 3 gig plan and she goes over by 4 gig in a weeks time it is . And this cost me an extra 40 dollars on my monthly bill. Luckily I caught it just as it was about to roll over 6 gig and charge me another 12 dollars . I was able to switch to 10 gig before that happened. Which now is costing me 60 dollars a month instead of the usual 30. Seems like this change benefits comcast and all the other carriers greatly as this not just an Xfinity or samsung issue it is widespread.
I am frustrated by carriers lack of response to this well know issue and it only affirms my thought that it is intentional.
Good luck to those having similar problems. Out with the old and in with the new isnt always a positive thing. Maybe if enough people complain they will figure out a way to solve it.
Ed
Ed

[DaveO3]

I am replacing my earlier post about RCS versus SMS/MMS as follows:

SMS/MMS texting uses your cellular connection (or WiFi Calling if it is working properly), never WiFi alone. Most carriers have size limits which area generally  either 600kb or 1.2 MB. Some carriers will attempt to compress a photo if necessary to send as an MMS, but if the receiving carrier does not support the compressed photo or the size of the MMS, it may not go through. Also, on the receiving end, you will not recieve any SMS/MMS texts unless you have a cellular connection or have a working WiFi Calling connection, never on WiFi alone 

If having WiFi on seems to be causing problems it could be that your phone might be trying to use WiFi Calling which is not working properly and is causing the problem, or your phone is trying to use an advanced messaging app such as google messages that is not current or not set up properly. 

[Installfraud]

Thank you for replying. I'm not sure why noone at comcast is able to explain as you did. People on phone support or in store seem clueless. Bad news is better than no news and endlessly searching for answers .
Thanks again
Appreciate you taking the time to reply