constant emails, not responding to an email

In July 2014 I a had given notice to my child's private school and had sent them numerous emails telling them I would be taking him out of the school in December and I wouldn't be paying December fees because of unprofessional service, neither of them had responded to my emails about this. I am now receiving constant emails from shapiro shaik to settle my account with the school in which they don't deserve because of their really bad service, the way teachers treat the children, teachers swearing at children and head of the school not doing anything at all. I had sent Shapiro an email explaining this and no response to my email, I get calls on my work phone which I keep asking them to call on my private cell due to this being a private matter and they don't call back when asked to phone on my cell. They threaten that I will be in bad credit due to a matter they know nothing about. I am disgusted in how this matter is being handled and Shapiro not responding. I think Shapiro should learn what the case is before constant emails and threats towards me. Please could someone resolve this fast