Billing Mistake!!

I have had multiple discussions with the support team:

I WILL NOT be paying the $400 charge for the defect home internet modem.

I was never,  nor did I say or accept this charge, and was never contacted in any communication about this.  I was online with technical service for a good hour trying to get my home internet modem working it was decided by these service that modem in question was defective and they would shipping a new one.  No mention of sending old one back.  No shipping info or pre paid shipping label provided.  I had no use for this defective modem there for it was discarded/ thrown into garbage.  Last month I spent countless minutes going over this with multiple people who were rude, condescending, more or less called me a liar. 
Take me to collections send me more bills.  I WILL NOT pay this $400.  Of this is not taken care of I will be cancelling my account, switching to another provider, and you can try to get those additional charges for my service and payments left on phone.  Good luck You will loose a customer, have unpaid bills, and do whatever you do when people don't pay.  I don't care,  I have had a enough of this f…ing total b….it.  Accept that your people in handling my defective device dropped the ball in setting up my return if this is your policy on defective modems.  I have no reason to be dishonest, there is no incentive for me to do so.  I am totally being direct and honest.  How you handle going forward is up to you.  I will not spend any more of my valuable time and emotion going over this.  Tim King mobile number on account 913-475-5092 - 1601 Elm St - Eudora, KS 66025