I am unable to receive messages

If you have an iPhone - and you are unable to send or receive SMS/MMS messages from your iPad - then you’ll need to explicitly enable text message forwarding on your iPhone.

On your iPhone:

Settings > Messages > Text Message Forwarding - set to ON and select your iPad from the list of devices.

https://support.apple.com/en-us/HT208386

Hi Team,

i am unable to send or receive SMS in my iPhone 6.

You are unable to receive messages on your iPad or on your iPhone?

This should go to the iPhone area. This area is dedicated to iPad and you will most likely get a better response using the iPhone forums.