Customer calls
Talking about some new feature he haven't totally thought about. so i tell him to think about it.
Talking about a bug, but can't reproduce it.
Talking about another enormous new feature but halt it after hearing the initial estimation.
Total time waster = 1.5 hours for every day.
DON'T LET CUSTOMERS WASTE YOUR DEVELOPMENT TIME.

instead of talking - use project tracking software (i.e. JIRA)