Royal Enfield — re350cc sprocket problem

Address:

560078

Date on incident is 11.12.2018

I am the user of RE350cc.. I have purchased vehicle on last march 2018..
just 12000 km decent city limit drove, now mechanic form Bangalore lalbagh road HSR service centre says the chain sprocket has problem and its not comes under warranty, and asking 3500/- for replacing the same, is this true. if yes then for what components 30000 km warranty is applicable..

I have attached the image of chain sprocket and supervisor chat snapshot..

you can reach me at venugopal.[protected]@gmail.com

i am requesting for refund of this amount if its comes under warranty