I always thought that "wo de ming zi shi ..." is the only correct form but today I found (and also a quite a few hits on Google" "wo de ming zi jiao ...". Is the latter normally used and correct?
First of all, I am not sure why the downvote on the question. It's a legitimate question at a basic level.
Now back to the question. Both are correct. /jiao/ literally "call".
/wo de ming zi shi .../ roughly translated to: My name is ...
/wo de ming zi jiao .../ My name is called ... (or, better, I am called ...)
I don't know why you thought the first one is the ONLY correct form. Perhaps it's what is in your textbook? Or it's what your teacher teaches in class? But in a language, it's very common to have more than one way to say something, especially something as common, and basic, as "my name is ...".
Welcome to language learning!
I'm an experienced Chinese speaker, and I totally understand your issue. "Wo de ming zi" (in Chinese: 我的名字） means my name is. Like in English, there are lots of ways to say "my name is". "Wo de ming zhi jiao" （我的名字叫）means "my name is called". In replying to @EmanAdam 's comment, both phrases are actually used very often in daily life. However, these phrases are mostly used in Mandarin, and not in Cantonese, which is a more "relaxed" style of language. In Cantonese, to say what your name is would be more like "我個名係...". As you can see, the language is much more natural to say. I hope you have a good time learning Chinese!