Cellular data is not working in my iPhone.

Randhal ~ 75% is not healthy and is almost certainly the reason for cellular data not working. Apple recommends having the battery replaced at around 80% – so have the weak, aging battery replaced and all will be well:

iPhone Battery Service

About genuine iPhone batteries

Repair Provider Verification

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

õ¿õ¬

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

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

Settings > Battery > Battery Health

õ¿õ¬