My Daughter Had A Tonsillectomy About Nine Months Ago. SHe

My daughter had a tonsillectomy about nine months ago. SHe is much better in herself as a result but she now frequently coughs up phlegm. This has always been the case since the op. I had assumed it would go away, but it's continual, regardless of her health and a loud conscious 'growly' cough to bring it up. Is something else going on?