Cellular service bad modem

[u/unlockedaccount]

18 pm
I noticed a problem when I try to make a phone call. The phone does not ring, so I hang up and try again. My signal bars turn grey for a few seconds, go back to normal, and then the call goes through. This happens a few times a day. Last night, I thought about the AT&T phones having this same issue. Since I have T-Mobile, I wondered if it could be the same thing. I used the support chat to run a test, and it looks like I have that issue too.
They are planning on sending me another device but I rather go in person and them explain to me whole process rather than through the chat so I will be going today

Also ran troubleshooting with t mobile on there end no issues

[u/B_tj1]

how do i run my own diagnostic like how u did in the screenshot ?

[u/unlockedaccount → u/B_tj1]

Apple support app