Billing errors without a resolution to the point of collection

For almost 6 months I've been calling, pleading, and complaining about the errors on my bill. We notified COMCAST via our business representative that we were closing one of our offices and wanted numbers transferred to another office.  I have emails to show this conversation.   The day that this was supposed to occur - our business representative was a no show.  We scheduled an online meeting and he didn't bother to show up.  I called customer service - over and over again, no resolution to the problem.  COMCAST actually disconnected my main office telephone number - you know, the one that shows up on business cards, signage, etc?  I had to call customer service again, and finally got the name of our business representative's manager who did help us - but not until March.  Well guess what?  COMCAST listed that since we didn't notify them 30 days in advance that we were disconnecting our office that they have billed us for 3 months of service for an office that was closed.   They also sent us UPS labels for equipment returns - and said that we didn't return equipment and were charging us for the equipment!  ARE YOU FOR REAL?  I kept copies of everything and got receipts from UPS for all equipment that we returned.  I have gone round and round with people including the manager, Stewart Tyrell and countless customer service representatives who say 'wait until the next billing cycle' and all of this will be cleared up!  I am now getting disconnect notices and collection notices for this bill that has now reached over $1700.  Is this how Comcast Business corrects its billing errors? By law, this is technically a violation of contract. I've been a patient and loyal customer, but my patience has nearly run out. Either fix the problem or compensate your customers for the errors that Comcast has made. Losing customers due to a billing and a professional service flaw (or lack of service) is bad for business.