<human>: Last school year in March, my class ordered about 250$ worth of books from Scholastic book club. Kids gave me the money. I mailed a personal check. We got all the books everything was great. I made a few more orders after that one, but all with credit cards. The check was cashed and my online banking has a record. The check did not bounce and was cashed timely.  

In June Scholastic started calling about an outstanding bill, I explained I paid and that the check was cashed, I offered to send proof. The guy on the phone said it was a misunderstanding that he cleared it up and apologized. He told me I was all set. I went on summer vacation. 

I have since started school and my mailbox was filled with collection notices and my principal is irate that she is now getting harassing calls! They had been calling my school phone all summer but obviously no one answered. Scholastic won't talk to me since it has now gone to collections and collections says they can't fix the debt since scholastic authorized it (or whatever the wording is). The collections people keep calling my school phone and it's a major headache. 

What the hell can I do? The collections keeps telling me my credit is going to take a major hit and to just pay it, but with fees and everything now it is over 300$. And I paid it!

Summarize the given text in a few sentences.
<bot>: Scholastic sent me to collections over the summer on a debt I paid by check (that was cashed). I am getting tons of mail and phone calls at school. What can I do to get this sorted?