Well im amazed at your problem because although altos engine is no way better than vitz, but onething is for sure that its tough as hell. Not good , but very good in terms of reliability and maintanence.
im sure one problem mightve occured, which had resulted in overheating of the car, and the rest wouldve been done by a cheap mechanic with cheap, yet ripping off solutions.
Ive been using Alto 2003 and to this day it has NEVER given me heating issues and i ALWAYS use AC (in summers of course).
My friend had the same problem when there was a water leakage and the engine got overheated.
I told him continously to REPLACE the radiator and get a NEW gas kit but yet repairs were done on the radiator and a new gaskit was installed, but then after a while the whole engine had to be rebuilt,
Funny thing AGAIN even after the rebuild, the exact same thing happened and i kept telling him to change the mechanics and get this properly sorted out but he didnt and sold his car off after the second rebuilt (poor guy but stupidly enough didnt change his mechanic)
So im giving the same advice to u.
Got to a SUZUKI authorized dealership. Trust me they are good.
get an engine rebuilt, get a NEW radiator and pipes (Even if its not leaking). A new radiator is very important (a long reply would be added as to why).
Make sure that their is no eating up of water after that, even lil bit cause thats the indication that the pblm hasnt been resolved.
Trust me , Altos engine is not powerful nor fun or a masterpiece but sure is very reliable. (its the same as potohar so definitely a succesful recipie)
Go to a suzuki authorized dealership and im sure ur pblm will be sorted out.