Tell if someone changed their number iPhone 5s-iPhone 6?

Okay so how do you know if someone changed their number, because every time I message this specific contact it sends as a text message the message turns green instead of blue and the other person has an iPhone so it should send as blue, and I've texted him before and it would send as blue and he would answer but now it only sends as green it's been sending as green for a few weeks now for that one contact and when I call the number it rings normally so anyone have any idea?

What the blue and green message essentially means on your end is one of two things. Blue means the message sent as an iMessage, green means it utilizes your texting plan and sends the message via cell tower. Also in some cases even if the person has an iPhone if they do not have iMessage enabled, the message you send to them would always been green. Other times if they are not connected to Wi-Fi the message you send them would also be green. Also if they changed their number sending a text message to that number wouldn't work, because it would be out of service.

You can't get it here, find it on some where else. No one having his number. You must also install Leo Privacy Guard to your Android phone, free available in play store.