I was all set to say, "No, it's not necessary to text before calling," but then I remembered that I almost did that today.
I was concerned that a conversation might run somewhat long, and I wanted to be sure the person I was calling had time. In the end, I decided to just call rather than texting first. I figured I could just ask, "Do you have a few minutes?" and if he didn't, he'd tell me. I called and asked the question, and he did have time, so we talked.
If it's a personal matter and it's during work hours, I might text first as a courtesy to find out if it's a good time for the other person to talk. However, that would be a rather unusual situation. I don't think it's required or expected to text before calling.