tone of voice on the phone

Am I being unreasonable to feel hurt when my son answers my reasonable request using a 'hard' tone of voice ? It's the sort of tone I'd expect from someone defending himself against an accusation. BTW he has a very good clear speaking voice.

I try to be brief, but I don't mind going into more detail about the actual phone call .I asked him was this a convenient time to call him ( late morning) and he said it was all right Then he said reception was poor where he was. I could hear him perfectly , not breaking up or faint. I never use a mobile phone, and wonder if this is possible with mobile phones?