iPhone texts going to email instead

My father is new to iPhones and smartphones in general. He has an iPhone SE and whenever he tries to text people, the texts going straight to their email instead of to their actual phone number.

I assume he saves peoples email to their contacts. I don't want to go snooping around in his phone looking at all his contacts so I don't know for sure.

But he has iMessage turned OFF so there's no way he can be sending it to their email using iMessage and he also doesn't have data so this is puzzling for us on why this is happening.

I assume (again) that he connects to his work's WiFi which is how its actually sending via email, if you understand what I am saying.

I've gone through the iMessage settings on the phone and found nothing on this. How can I fix this and stop the texts going to peoples emails for him?

I've tried stuff on other posts but it didn't seem to work. For example; someone said that when you create a new conversation with someone, you might have started a conversation with the email address and one with the phone number. That didn't happen with him. There's only conversation and it doesn't say if its email or phone. Some times it goes to phone and sometimes it goes to email. (The text messages I mean)

Given what you have said, the other people must be sending messages to your father from their email, so you will need to check what the other person's address/phone number is. If he wants to text them, and not email them, he will need their phone number and not email. I suggest you add a screenshot of the contact information of your father's friends, but it is likely the other person's Contact information includes an email but not a phone number.