Before I go out and buy a volume controlled phone - the best start at $100 - I thought I'd try an in-line amplifier first. Mom complained of echos and static on the phone so I hoped this would fix that and it did. I spoke with her for more than 20 minutes and only had to yell once! It was a huge relief. I still need to get a phone with volume control on the handset or receiver but this will help reduce distortion on the line and boost the volume for Mom too.
I found the following product at walmart.com. I usually don't like to shop Walmart but they had it for the best price and I could have it sent directly to Mom's apartment. I should add that it takes a couple of AAA batteries but the first ones are included with the amplifier. I also liked that she could adjust the volume on the unit.
Clarity CE-125 High Frequency Portable Telephone Amplifier, US$14.82.