Thank you for your query.
I understand your concern.
Your child is probably suffering from an infection which is not responding to the above mentioned antibiotics.
Your child needs a powerful antibiotic sensitive to the ear and sinus infection
He needs vapour inhalation,an antiallergic and nasal decongestant along with it.
It should take a week to heal .
Kindly consult an ENT specialist
If you have any further queries you are free to consult me.Hope this answers your query.Wishing your child a speedy recovery.Have a nice day.