Change iOS settings

Please describe the problem you are encountering with your iPhone 7 Plus in a few more words.

Does this iPhone 7 Plus have its original battery?

(See: Settings > Battery > Battery Health of 80% or lower is headed for battery replacement.)

Also, depending on what is happening here, try this: Force restart iPhone - Apple Support

What seems to be the issue with your battery? How do you know the battery is the trouble here?

kabir189 wrote:

Battery problem

Is the battery health 80% or lower and thus headed for replacement?

See: Settings > Battery > Battery Health.

80% or lower is headed for battery replacement, or for iPhone replacement.

For details: iPhone Battery Repair & Replacement - Apple Support