So I had a Galaxy S5 for years, loved it, never a problem. But since the kiddo upgraded to a Galaxy S9+, I decided to get the Galaxy S9. That was 2 months ago. Mobile data has been a HUGE problem since day one. Like 67mbps download on wifi and about 27mbps upload on wifi. Turn the wifi off - and you always get about 3-4mbps download, and usually about 0.11 upload speed. Text messaging barely works. Attaching an image is useless, it'll never go through. Download from the Play store usually only works when on Wifi. Basically, the internet is all but dead unless on wifi.
I went to the ATT store on day 2 of owning the phone, and they wouldn't help, since I bought the phone from AT&T's website. WTF? So they dialed the 800# for me and passed me the phone. That's the honest truth. That ended up with no fix. I bought a new sim card, same problem.
They have simply opened ticket after ticket and made me reset to manufacturer's default endless times, even though I knew that wouldn't fix it. They send me to some "u break it, I fix it" store that they work with, they couldn't do anything. Even their OWN techs when looked into it, couldn't remotely work with it (yeah, no upload speed!). But they refused to do anything but troubleshoot. THEN they tell me, oh, well you had it for over 30 days now, so it's past "our" warranty and you must use blah blah blah blah....
I got a little upset to say the least, with our 4 devices and 20 years on our account with never a late payment.
The new phone will be here in 2 days with a new sim card.