i am not getting the 4 digit code for two step verification in my iPhone 6

Did you already check this thread about it?

Re: 2 step verification with find my iphone

This help article also covers the steps:

Apple ID: About two-step verification and SMS

You're welcome 🙂

I hope those articles can help, if not come back and tell us what steps you took that did not work.

In Australia at least, the 2 step verification code comes from a "Premium SMS" service. Vodafone blocks receipt when sending is blocked.

See this page SMS phone number verification for UK, Ireland, and Australia - Apple Support

Check you can send "HELP" to the SMS number listed on the page above. If it won't send, it could be that you have "Premium SMS" blocked - for sending and receipt.

Apple tech support didn't manage to solve this one for me, but the failure to send provided a clue.