A+ Pest Control

We had been with A+ Pest Control for years. The service had gone down significantly and we cancelled. They sent out a technician after we cancelled who started work without coming to the door, and without our knowledge. Once he came to the door to have gate unlocked I told him we had cancelled. He told A+ Pest Control that I refused to sign paperwork which is a lie! I would have corrected any information on paperwork and signed, as I have done this with other companies. We received a bill and called and asked to speak to a manager. They agreed to remove the fees. We have an email dated 7/5/19 stating we have a $0. So we thought it was resolved and moved on. Late December 2019 we receive a collection notice from Okrin (who we have NEVER had!). Once they look further they say it is actually from A+ Pest Control and I will have to talk to them directly to resolve. I had not received any further bills or notices or anything! I call A+ Pest Control and the billing person had already left for the day (at 1pm) and would call me first thing in the morning. NOTHING... We call again first week of January. Response we got was "Well you owe for the work the Tech did." (First, we had already cancelled. Second, he did NOT do a complete treatment.) Send me a DETAILED billing of my account. We receive a Post-Dated Invoice. I know it was post-dated because I have an email after the date showing we have a $0 balance! How do I know they will not continue to keep creating invoices and charging me money or threatening to send me to collection?