Can I be sued, or in trouble for selling a used phone from verizon on craigslist that verizon locked?

Never once to my knowledge would I have assumed if you let your account lapse, that Verizon would lock the phone. I listed the phone, and someone purchased it, came in, looked it over, and handed me cash. The listing itself just listed a phone for $70.00. I had not known that it would be locked while I was in a dispute with Verizon, and had opened a new account with sprint. Hence the reason I had sold the phone. Now the buyer has let me know that he is filling a police report, and sending my company (where he came to purchase the phone) slanderous letters letting them know I sold him a "lost or stolen phone" which was never the case, it was MY old phone, that I listed since I had no use for it.