Honestly if your city has a 311 style thing, I'm not sure there's a ton of need for an LLM. Eight or nine years ago my grandmother visited me in New York and accidentally left her pocket book in the cab. Since I had paid for it with my credit card, I was able to see the medallion number in the transaction, so I called 311 and said that I wanted to get in touch with a specific taxi. It prompted me for the medallion number, which I told it, and then it transferred me to a call with the dispatch service, who then transferred me to the specific garage, and they called the driver and told him to call me, so we were able to meet up again and get the pocketbook back (turned out he returned to where he had dropped us off to try to find us, but since we only had a short stop there, we took another cab back to her hotel after, so we were gone).