2007 Toyota Camry Air Conditioning

I have had problems for the last 2 years with my Camry blowing warm air out
of driver's side vents. No leak could be found and I kept recharging the freon
until that didn't work. 1 month ago I had the evaporator core replaced. It
worked for 2 weeks, then started blowing warm again. I took it in and they
"fixed" it. That lasted about a week and it blows warm from both sides.