chat app that works with Siri

I regretfully have to be without my iPhone in several weeks. The problem I am having is that I have my sim card in my iPad but that only allows me to use data.
My staff has no iPhone, but a samsung, that is officially the worst phone they have ever had.
I need a chat or messaging app that works with Siri. Because when I am on the go it takes so long to message.
I am having a bluetooth keyboard but I use Siri in iMessage to be able to do it quickly when I need to.
They do not have Facebook or such things.
EWhat I essentially need is a chat or messaging client where you don't have to have another account or phone name. I just want one account.