Ask HN: How do I hide my private information to apps?

Hey,

I was out with someone I met. So after we had a coffee etc we said lets exchange numbers.

I am doing a misscall to him and he had an app that literally spitted out my email address on his phone...

I feel very unsafe after that. I am using gmail and I understand the implications on my privacy using google as my provider but thats just too much...

Why would a random app be able to connect my mobile number and my email together, and how?

How do I take it off?

Any help is much appreciated.

(I've no idea what the app is called, he was using an android phone) Update: I think this is the app https://play.google.com/store/apps/details?id=com.truecaller&hl=en_GB