iPhone 6 Plus shows “no service” or searching

See if the following support article can help:

• If you see No Service or Searching on your iPhone or iPad - Apple Support

Maliktan wrote: "The iPhone battery is original and its health is 90%."

80% is considered to be the point at which a battery is regarded as unhealthy. So 90% is surprisingly good for a 7 year-old battery. So good that I wonder whether it's accurate. You could ask for Apple's opinion/help here:

Get Support

And in case you want to have the aging battery replaced anyway:

iPhone Battery & Power Repair

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Maliktan ~ Does your iPhone 6 Plus still have its original battery?

And what's the Maximum Capacity % here?...

Settings > Battery > Battery Health

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