Why does no one know what they are talking about?

I took my 5g home internet modem into a corporate owned T-Mobile store to cancel the line and return the device since switching to T-Mobile Fiber about a month ago.

The rep told me there was "no need" and the modem would continue to provide service for when there is any kind of fiber outage. I double checked with the manager, but I was told there was no cost for this.

I get my bill the other day and see my previous 5g plan, previously under a business account, was not only still on there, but charged twice.

The Fiber agent who sold me the plan told me she had been with T-Mobile for like 10 years and when switching from a business to a personal account, told me none of the current discounts would "be affected".

I call into 611 and the agent told me at first that yes, the backup plan was supposed to be free, and would change it for me.

On hold for 10 minutes, she comes back and tells me it's not free, but in fact $20 a month.

I don't know what has happened with T-Mobile, but I feel like ever since the sprint merger, so many people in customer service have absolutely no idea what the fuck they are talking about.