In re: 'जले हुए कारतूस' which can have minor utility through improvisation.

There are useless people who were useful in the past who try to stay relevant by making tall prima facie false claims.

Some such people cannot be completely discarded because they could retain some residual use.

How does on deal with them?

Simple:

• Ignore most of their calls/messages,
• Answer them sometimes,
• Avoid meeting them most of the time, 
• Meet them on rare occasions, hear their nonsense, tell them that you will get back but obviously do not waste time thinking about what they told you after they leave.