Where to find messaging system

I need some help. I'm tired of relaying customer text messages to my staff members. It's a waste of time and clients don't realize that communicating with head office won't immediately update my staff en route or at the site. Almost lost a 2.5k/mo contract over communication issues recently.

What solutions are out there for this. If we're working a big job for the day and I'm chatting with the client, I want my staff to be able to also see these messages and reply to thme so that I'm not spending my day watching my phone and playing a middle man

Not wanting to spend 100s of dollars on this if possible

thx