Unknown number Call disconnect

Hey I bought this iPhone XR from USA and now I’m using here in India. I have been observing that if I receive any unknown number call then call is automatically disconnected. I don’t know why? Due to this I had missed many important calls. Currently I’m using Vodafone network. I’m facing this issue since last 6 months. Is there any Mobile settings for those mobiles bought from USA?

Could you please help me out?

Awaiting to here from you ASAP.

Regards,

Deepak K.

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