I know Teams doesn't live on the intranet, but I'm not going to put work software on my own phone. Policy needs it to set up a work profile and I then can't use fingerprint, face or a 4 digit pin. And all the shite that flows through Teams would be be piling up, just like it does on the PC at work, brilliant when you're only in a couple of days a week. They want me to use a phone? Provide one.
The WhatsApp group is for us to send updates about traffic, if someone can cover a shift etc. it's not an official work thing. I could of course not use it and just text people. That's really just making my life difficult whilst sat up here on my high horse with a self righteous look on my face, whilst I miss the chance of an extra shift.
Denying putting work stuff on your phone is absolutely valid. The company should provide a company device in that case. And if you do agree to put company data on your phone, they should give a monthly stipend towards your phone bill. That's how every org I've worked at has approached it.
Really depends a lot on the groupchat. I was apprehensive but it's quiet there and overall the things that get sent there are either in office hours (e.g. "internet might be out intermittently we are working on a fix") to links to pay for something someone paid for outside of work like food or drinks.
I don't mind it that way, maybe once a week a couple messages
…to which for privacy reasons your team shouldn’t like SMS, Discord, Telegram, Slack, and probably even Signal (somewhat for privacy, & more for accessibility)
XMPP. A business can self-host, there are public servers, or there are many businesses which offer customised xmpp hosting as a service.
I can be federated with other xmpp servers or be a locked-down work-only service, or federate with chosen other servers (such as a client company's xmpp servers).
If that's the main problem then that's easy to solve! Simply use a free public xmpp server.
I mention the self- and paid-hosting options because businesses tend to like having a sevice agreement backed by a contract, and may have additional specialised requirements not provided by free services (xmpp or otherwise).