No 4G data
I recently bought a Blackview BV9900 Pro unlocked phone. I went to the ATT store near me and got a new sim card for it. It was working perfectly fine for 4 or 5 days. The just today, my 4G stopped working. At best, I can get 3G data to work. I have tried manually entering the APN setting, selecting 4G network, and resetting my network settings. Each time, I restart my phone. I am very frustrated at this point. Could you please advise me what to do.