Suddenly unsupported modem?

I'm no expert but I think that if I subscribe to a new ISP and use my still relevant 5G CAT11 capable Hauwei B618s modem, and that it WORKS!, but then 20 minutes later you kick me off the network telling me my modem is no longer supported, while it clearly was working perfectly well....at least a month ago when I asked you, but you suddenly go and change the rules to what I can only imagine is some kickback scheme from modem manufacturers that can't sell their new modems? Or I don't know, according to many a search your list still include those now kicked modems, and your website is misleading because the modem you show for sale at a discount appears to be from the old now unsupported list?? I mean....huh?? Why is this happening? Someone needs to explain why I am forced to replace a perfectly working modem now with another for plus minus R4000?! It was ON and functioning...then YOU turned if off....explain, I will fact check. Correct me where I am wrong, I would love for this to make sense. Please.