Servicing some time can reveal problems for instance maybe the dryer bottle is chocked or the expansion valve needs to be changed.
And you can clean the condenser from outside but for cleaning evaporator you have to open up the inside box.
So servicing improves cooling.
BTW try not to use the fresh air option in the car its better to open up window than using fresh air.
If you are a frequent fresh air user than your evaporator needs more frequent service.
Hussam, Liana's a/c works fine you need to get your A/C checked. How old is your Liana? and whats the mileage?