AC on my 2004 Buick Lasabre is not working correctly as I had my Freon checked and it is very Good and when I pur My AC on Low it works but if I try to use it on high it does not increase the cool tem

Sound like to me that need more freon there is a few ways of doing this so best way is with car running with gauge ac on it should read in the green part of your gauge if you have a gauge from a normal freon can from walmart ect. even so its in the green you might have more air then freon on the system and might have to take it to some place that does ac and ask them to re run it through so they can take the air out also vechicals have a orifice tube that can dirty and slow down things like cooler temps and this is helps remove air from your system lask i check so that might be somthing to look into also if you change this you should have the car refilled with freon for a profionnal to get your maxmal proformace from your ac not ouf of a can you can also have them put dye in there to find leaks to save you money in the long run good luck