how service center make full to customer ?

Location/place: nallasopara

Name of company/service: Synergy Enterprises

I am using samsung galaxy s plus. i was facing a problem like the applications get closed automatically and the backlight gets blink so i go to the nearest sevice center of samsung as my mobile is in warrnety period,as i go there they told me that there is problem of software ,so u hav to update ur software .i said ok and give my phone to them for updating.when i go to collect my phone they told me that ur phone’s USB connector not working which is already work in my house ,i said ok change the connector and give my moible.after collecting mobile the phone is in good condition that time the phone work normaly,as i came to home i found that the problom which i faced is not resolve.again the next i go to the sevice center for same prob they told me that you hav to keep ur mobile in service center for 3-4 days and there is problem of motherbored.before software updation my phone is fully ok but after the updation my phone faces lots of problems.so i request them to replace my phone as it is in warryenty period they said ur phone doesnt get replaced if u want u keep ur phone there i repaired it again.there for i call to customer service staion i told everything about the company and i was shouck when he said that they didnt hav any information regarding this sevice center.(i am fully sure that the sevice center change the original parts of the mobile as u give for repairing).