5G signal, can't text : (

Hello-

I have a Samsung Flip 5G on T-Mobile.  With this phone, I've been having difficulty with texting for some reason over the past several months.  About every day this happens.  I'll send a text, and the text will "hang" then not send.  I'll get the little spinning circle in the lower right corner of the text, then after about a minute or two the text box turns grey and I get an orange exclamation mark on the lower left corner indicating the text didn't send.  I'll have to reboot, then usually the text will send.  

Why is the phone constantly doing this?  My phone will either be on Wifi with a strong signal or showing a strong connection to 5G, 4GLTE, whatever, and I'll get a message saying the phone will send the text when it gets "back on network" or a message similar to that (I don't recall the exact message).  It's pretty frustrating to have to reboot my phone once or twice a day to send text messages : (  Thanks!