Hello Saritha and thanks for the query
Its not good to use antibiotic so often in children. Try to rule out the cause which is causing recurrent cold
. Firstly go for steam inhalation and lukewarm water gargels and try to expel out the phlegm as much as you can.
Try to protect your child from changing climate and wet cloths.
Don't allow him to drink cold water, cold drinks, fried or oily food and chocolates.
Keep him in Hygienic environment
The cause for recurrent cold may be Tonsillitis
, Unhygienic environment, Respiratory Track diseases etc.
Consult your doctor and rule out the cause and follow the instruction.