OnePlus India — the ringtone is not ringing.

Address:

Jakhandevi, Almora, Uttarakhand, 263601

I purchased a mobile handset one plus 7 pro on 16/08/2019 from mangal sales ava's vilas choraha haldwani. When someone called me the ringtone was not ringing, since then i am trying to fix the problem but the phone continues to be in vibration mode. The ringtone volume key on the left side of the set is showing maximum volume but in settings the ringtone volume is not working. Please help me. Thanks a lot.