Network problem

misgoo wrote: "I bought used. once reset the setting and then hard reset the LTE will work, then suddenly it will back to 3G"

misgoo ~ Again: How many years ago did you buy it?

Also, as you bought it used, and now at 88% health, the battery is likely to have been replaced. So did you buy it from a reputable source such that the battery would be genuine?...

About genuine iPhone batteries

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misgoo wrote: "Sure it’s original battery with 88% battery health (...) yap, the battery is genuine as far as i use it.(...) around 1 year ago…. From my friend"

When you bought the iPhone 7 from your friend, did he/she say whether the battery is the original or new?

...If not, he/she may have had the battery replaced – as implied by the high 88% health. And if it's not a genuine iPhone battery, it will be weak and so may be the reason for your network problem. So I suggest you ask your friend whether the battery was replaced and if so, by whom:

Repair Provider Verification

...If the repair provider doesn't get a big ✅ from that verification site, you've got a weak, fake battery – in which case:

iPhone Battery & Power Repair

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misgoo ~ As the original owner said it's the original battery and you said: "Sure it’s original battery", there's only one case, not two:

The original battery of your iPhone 7 is old and overdue for replacement. So have the weak, aging, original battery replaced:

iPhone Battery & Power Repair

About genuine iPhone batteries

Repair Provider Verification

(Articles found by searching Apple's Knowledge Base.)

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misgoo ~ 88% is unexpectedly high for an iPhone 7 original battery...

Did you buy your iPhone 7 new or used / second-hand?

How many years ago did you buy it?

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misgoo ~ Does your iPhone 7 still have its original battery?

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

Settings > Battery > Battery Health

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misgoo ~ You haven't answered either of these two previous questions:

How many years ago did you buy it?

...did you buy it from a reputable source...? (eBay is not a reputable source.)

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