Am I wrong to be irritated?

My husband along with his kids live in a different state than his children's mother, so they skype with her as a means of communication. Well, I just saw on the computer that we share that he was skyping with her while I was in class and his kids were at school... for 20+ min. Supposedly his excuse was that she was in school and couldn't talk on the phone. Surprisingly, after their 20+ min skype session they talked on the phone for another 30 min. This really aggravates me because there wasn't a valid reason as to why it was necessary when a phone call is enough. And to make matters worse, he plays the victim as if he's not good enough. Am I wrong to be irritated?