I've see such on my old iPhone 6 and my newer Moto G. The number of bars are sometimes meaningless and I can hit 4G and as I travel it falls back to 3G. I've learned over time to not lock my phone to just 4G service and think nothing of a reboot.
Hello CNET, I was wondering if you could help me with a problem revolving around the data usage on my phone. About 24 hours ago, the bars on my iPhone 7 Showed that I had zero bars of service. The weird thing was, it didn’t say I had no service, and I could pull up YouTube videos at normal LTE speeds. However, I could also not receive any calls or text messages during this time. This almost caused a dilemma a couple hours ago. Even More strange Is that the problem fixed itself after I went in and out of a no service area, but my Internet was running super slow, so I restarted the phone and everything is working properly now. I see that this is notA real common problem, seeing that everyone else I saw on other forums revolving around #DATA use said that they could get barsbut couldn’t get Service. I’m wondering if I should get my phone checked out. If anyone could please help me, I would sincerely appreciate it. Thank you

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