What do I do about my mom’s landline?

My mom (82) has a landline that she insists on keeping due to being in a church group that takes calls for prayers and the calls are taken on that line. She has a cell phone but she absolutely does not want those calls going to that.

The problem with the landline is that the majority of calls are scammers. Most of the time she is smart enough to let calls go to voicemail first but on occasion she doesnt, and sometimes falls for the scam.

On two occasions (that I know of) she has ended up buying iTunes gift cards, or in this recent one, paying them for something she did not buy nor would she ever order. She fell for a spoofed number that had her same area code and that's why she picked up the phone. Fortunately, she had the wherewithal to call the credit card company immediately after the transaction to get them to cancel it because she was suspicious.

The problem I am trying to solve, is how do I give her a way to maintain her prayer line but get rid of the landline, or some way to limit or filter the scammers better. Has anyone had to do something like this?

Also bonus if you have any resources that you've shared with parents about phone scams that was easy for them to understand.