iPhone bought off Craigslist Blacklisted after * months use and Verizon reps approval!

Keep using it Iike I have for the last four months ... I have a serious complaint to be known and would like a resolution. I have a business account and on one of the lines I purchased an iPhone X off craigslist. Before purchasing it I contacted our Verizon business rep and asked if this phone was ok to use, I was told it had never been activated on an account and should be good to use. I purchased it April **th and activated it that day. It has been activated the whole time until August **th, on this day I was looking to buy an iPad and had to verify it would work on Verizon so I inserted my iPhone SIM card in the iPad. I discovered the iPad had an activation lock and did not buy it. When I put the SIM card back in the iPhone it didn’t work anymore and my line was suspenseded. After * trips to Verizon store and * calls to Verizon tech support (more then * hours total time involved with each telling me different solutions and none of which were correct) I was told the iPhone was blacklisted because it wasn’t paid for by person I bought it from. This now leaves me out $*** I paid for the phone, * days I couldn’t use my phone because of store and tech support not giving correct info, missed customer calls, and having to buy ANOTHER phone. Had I not used the sim in the iPad you would not of known and I could of kept using it, I guarantee you have sent the original account to collections which You’ll get paid from, the fact I do have * lines with you and have purchased several phones from you already, this should count for something. If you truly value your customers business you are not showing it, you won’t get the phone back, you will get paid by collections, I am paying for multiple lines so why not allow me to continue using the phone?