Sounds like things have changed since I was there a few years ago. No Bulgarians I knew really had conversations on the phone since it was more than a lev a minute. No one had plans. They just bought vouchers. Text messages were 15 stotinki, so it was more efficient and inexpensive to just text. I did notice that people would answer their phones on buses, which was annoying. In contrast, I visited Japan the same year I lived in Sofia. In Tokyo there were rules against talking on your cell phone in the trains. No one had to regulate this rule, people just obeyed it. 
I like texting, but I find that it is a protective and impersonal way to communicate at times. It's good for setting up places to meet or reminding someone of info. But I will usually call the person if we exchange more than three texts. I like to hear people's voices. However, I know this is foreign to those who are 25 or younger. I once watched my high school cousin have a conversation with a girl via 80-plus text messages. Talk about sore thumbs! :)