Geico cancelled our auto Insurance!

We recently received a letter from Geico insurance stating they had to cancel our auto policy because we do not have a "permenant address" . We have been in the same rv park since last July and have had the same PO Box. We have had Geico insurance for about 7 years and have lived in 3 states during that time but for some reason they have decided to get rid of full time rver's. Has anyone else had a problem like this? We have never filed an insurance claim and have perfect driving records and always have paid on time, so I feel this is very unfair treatment.