DPF warning light on 2016 deisel auto

hi all,

i‘m new to the forum and hoping someone can help me with my problem.
I bought 2016 CRV 2 litre deisel auto only a year ago and warning light for DPF has come on.. As I understand this covered under warranty as car is just 2 years old however Honda have come back and said it won’t covered under warranty as I have not used the car as recommenced that is average of 25-30 mph.. I have been using the car normally and average is 13.9 mph over 8000 miles .. however I was never told of this requirement of driving at 25mph average speed nor can I find anything like this in Honda warranty book..

can someone please advise me my options as I feel really let down and short changed as it should covered under warranty.

thanks in advance,
santosh