How can I stop my mom with Alzheimer's and dementia from using the phone and calling places she shouldn't be?

Could I get some suggestions what to do about Mom calling places of business she shouldnt be??? I know I need to have a phone for her to use in case of emergency, so I cannot take the phone out of the house. But, I want to limit WHO she can call or receive calls from during the day in case she is alone...I stay with her most of the day while my brother is at work but for the day(s) when she is alone for a few hours, I need to limit who she can call or receive calls from....is there a phone or a device that can do this for me ??? I have started to look online but I was wondering if anyone has found a certain device that would do take care of this issue for me...I am already her DPOA and she is causing alot of confusion and unnecessary extra work by me having to clear up from her phone calls..... any advice I can get would be greatly appreciated....thank you