dust in front camera

i am using an iphone se and it been 6 months using it i around 20 days back noticed that there are a lot of dust particles inside my front camera , i told service center and they told me to backup my phone and handover to them but the thing is i am afraid to hand my phone to them to examine as i had a very bad service experience with oneplus 5t also where they just blamed on me that my phone was out of warrenty because i had made it get repaired from a local market (which i havent ) as i wanted to do so why would i then go to there service they told that if i want my phone to be repaired i have to pay20000 rupees as motherboard was defected

so for me why belief from service center is gone

also apple service center B2X also dont have a good service record according to google reviews

i live in jalandhar

and i also wanna ask why is this dust problem occouring