Telephone Distortion Effect- your thoughts

I use a Ameriphone XL 40 telephone. This phone has strong variable amplification. It also has adjustable tones.

The problem is and please correct me if I am wrong- my hearing aid already has been adjusted for for my sensori-neural loss. If I use the XL 40 i have no way to neutralize its adjustable frequency tones. I do not need dual frequency tone adjustments- just dual loudness (my hearing aid and the phone.).

It is my thinking- dual tone increases distortion.

What are your thoughts/experiences?

thanks in advance