Hi my name is ***** ***** I will be the expert working with you today to help and resolve the problem you have posted.
I am sorry to hear that you are having such trouble. I will try my best to help you out and resolve the problem as quick as possible.
Let me know the make and model of the phone she is using now which has a problem hearing.
on the base you can see the model number let me know that so that i can provide you the correct steps to fix the problem.
not sticker on the handset or on the base?
Without the make and model its difficult to identify the hardware however if you can click a picture of the phone and post it here i can try identifying and then we can proceed if you like.