I have had persistent sore throat for about two years now. Please how can I get a permanent cure for this infection.

Need an ENT exam. To know how to treat, one needs to know the cause of your problem. This can only be determined by a direct examination by an ENT doctor. The most common finding in this scenarion is reflux, or gerd. Prilosec otc, anti-acids, elevating upper body at night, and low acid diet all help.
Sore throat. See an ENT doctor... Tonsillitis, gerd, sinusitis, allergies all could be involved.