2015 nissan sentra- a/c only blows cold at highway speeds

I have a 2015 nissan sentra. When i first got it in 2015 it had one of the best ac systems i had ever had the pleasure of using, like too cold in 105 degree heat on the minimum setting. Then after about a couple years a lady on her cell phone caused a 6 car pile-up and i was car number 4. We took it to a body shop that was at her insurance company’s same building, which was fine with me because it was kust down the street and had a good reputation. Well after theu had it for a month i got tired of the rental (2015 corolla) so i called them and said i wanted to pick it up it had been far too long, the guy said you cant its not done so i asked what still needed to be done and he said just the badges. I told him not to worryabout it that it doesnt matter to me, he still got upsetabout it and eventuallyi said look man its my car im coming to get it badges or not and id sign something saying it was done to my liking, he got pissy and said fine it will be put front. I pickedit up and didnt notice for a couple days because it was mainly highway driving i was doing at the time, but i noticed that it just didnt blow as cold as it used to before the shop had it, and that it slowly started cooling less and less in city driving conditions, todau it was 106 degrees andI am only in city driving conditions these days and the air coming out is about the same as the air temp outside maybe a little bit cooler but definitely not cooling at a satisfactory level. When i drive highway speeds its get cold and is bareably cool but still no where near as cold as it used to be. Do you think the guy let out some freon to get me back for picking up my car before he wanted me to? What can i do to find out if its got a low charge without gauges? And what other things could be contributing factors or causes? Sorry my question is so long but i feel like the more info the better advice or dianosis you all can give.