For customers that are unable to hear the phone, or unable to speak for any reason will be able to get s special plan. You or someone using your phone can only dial 911, and 988. No other outgoing calls will be made. This saves the issue of someone using your phone for not so good things. Incoming calls will be provided with an announcement to communicate with this person through non-voice means, and calling this number will do no good, nor even go to a voicemail box.
The best way someone can communcate with a non-verbal customer will be through RCS?/SMS?, or another platform. The plan costs the same as any other cellular line. Since the non-verbal plan is for everyone that would not be able to communicate might also be hearing impaired, this is why there is no voicemail services. By having an announcement instead of leaving the caller hanging, they will know what to do.