Using iMessage on Wi-fi only device

How can I use old iPhone 4S iMessage over Wi-fi only...

I am borrowing a friend's old iPhone 4S to use as a Camera and Wi-fi only device in Italy for two weeks. After much ado, I set up a new Apple ID, erased hers from the iPhone 4S, added mine and logged into my email. Email now works - to and from the Wi-fi only iPhone 4S.

However, I cannot get iMessage to work under my new Apple ID. It used to work with my friend's Apple iD, but all of my messages show up on her new iPhone 6. The iPhone 4S still registers her phone number and says the carrier is Verizon, although it is not connected to Verizon. Her phone number is active with her new iPhone 6 on Verizon Wireless.

I want to use iMessage from this Wi-fi only iPhone 4. Help! iMessage is frozen at "Waiting for activation". I should be able to use iMessage from this old iPhone 4S over Wi-fi, right?. I have an iPad Mini at home (Wi-fi only) that I can iMessage to and from quite easily.

Any insights? I would love to use this in Europe for two weeks.

Version 8.2

Model MD277LL/A

Daphne