I assume you mean work uses SMS/MMS and does group messaging with it?

First, a business shouldn't be using SMS/MMS. It's a best-effort "protocol" (it's not really a protocol, it's a method of injecting data into cell management frames), which means it'll try to send, and maybe it'll get there. There's no store-and-forward, no error checking/correction, etc. It was never intended to be used the way it's being used.

Behaviour is dependent on the service, device, and app used (as you've experienced). As others have mentioned, using a client that has a setting for treating Groups as "Chat" or something similar, will address the problem you're seeing. But if anyone else uses an app that's not setup this way, the problem will exist with their replies.

Pulse, Textra, Handcent, etc (pretty much every SMS app I've used) has this setting.

Also, don't set your MMS limit to some arbitrary value - set it to what your cell provider has documented as their max, or less. Setting it higher may cause messages to appear to send (since it's best-effort with no error checking), but the back end may simply drop it from being too large.

I've seen this on MVNO's and on Sprint, TMo, and one other (ATT maybe?). Verizon doesn't care about size, but some of it's MVNOs/resellers do (Xfinity/Visible, etc).

If you can, try to promote a better messaging solution. I'd never entrust my business comms to SMS/MMS. There are business plans for Jabber/XMPP services, for example (probably best to outsource this, if they think SMS is OK to use), with iOS, Android, Windows, Linux and Web clients. Plus, Jabber/XMPP supports voice/video calls through the app, if that's something they could use. (I say business plans, because they surely don't want to manage this themselves, and by having their own server, they can manage users, rather than make people sign up on their own at other hosts).

There are other messaging systems they could use. Jabber was the first that came to mind, and being an open protocol is unlikely to disappear or suddenly change in a negative way.

Edit: A significant benefit to Jabber/XMPP is being logged into your account, simultaneously, on multiple devices. I have 2 phones, a desktop, a laptop, and an iPad, all logged in. I get notifications simultaneously on all of them (it's configurable), and I can reply from any device at any time - my replies show up instantly on all devices.