creditor harrassment

Pa.
Recently canceled my cable service and paid bill in full. Now receiving calls from collection agencys telling me I owe money for early cancellation of contract. I contacted cable company and they said, I do owe more money. I said, my balance is paid, my bill reflects this and did not show this cancelation fee. They said, this was handled by a different department. Now I received a letter in the mail from a collection agency saying I owe money and have 30 days to dispute.
My questions are!
The cable company never sent me a bill and it is not 30 days past due. So how can it already be turned over for collection?

The letter says I have 30 days to dispute the validation of debt. So how can they be calling me when it is not 30 days overdue?

One of the callers won't leave a message and when I hit redial I get the operator saying the number is no longer in service. The next day, I receive another call from the same number. This goes on every other day. I filed a complaint with the better business breau againist the cable company for this harrassment. Can I file a complaint anywhere else and is this a harrassment case?

Also are there certain state rules in regard to early cancelation contracts?
If so where would I look for them?