if the infection is on the frontal sinuses, you need a top quality ENT specialist. Ask for a professor. The standard ENT blokes can't deal with frontals, trust me i know, mis diagnosis of a frontal infection has cost me 10 lots of surgery and still no solution. If it is in the frontals, you may need a Lothrop to clear it (drill out). Get it done quickly as infections left untreated can get into the bone (skull base) and are hard to treat (my current issue).
Trust your instinct. If you know there is a prob and are getting no where ask for a referral to the next rung up. Demand it if you have too. You want the best ENT specialist looking after you not one of these local guys who do a great job on the basics but are out of their league with anything more complex...