Dynamic values in Jinja templating

I am building a message which I want to send as SMS. I created some fields where values can be inserted. And created a template in custom doctype as

<p>Hello {{doc.cust_name}} </p> 

but its not fetching the data of customer name. Any approach to do so. Also one more thing, I need to send this generated message to mobile. Will it be properly visible on device .

Thanks in advance