It is important to know for how long you have cough
, colour of phlegm (mucus). Do you have any nose problem, heartburn
, any chest problem?
If it is there for more than a month then a doctor has to examine you to find out the exact reason for your productive cough. Then only treatment can be initiated for cure of it.
For this you can see an ENT specialist
If the duration is short but more than a week then you may need a course of antibiotic.
Then you can approach a GP (family doctor).
Wish you good health.