How can prevent someone from getting and receiving calls from multiple phone number

My husband, (we'll call him bob for now) had a brain injury some time back. He now has massive dementia-like symptoms that came on suddenly and have left me scrambling to get control of everything including his phone usage.  He receives hundreds of texts messages and calls a day from con artists and scammers trying to convince he's won a car or the lottery. I need to block the numbers, but he won't let me near his phone.  I am the primary account holder, but I need to do this in a way that he's not alerted by T-Mobile that anything has changed with his phone.  If he knows I put any kind of block on his phone he'll have a meltdown and that is dangerous at this point. Can anyone advise me on the most discreet and easiest way to do this?  Remember there are hundreds of numbers - I just found them all on the billing online.