I don't know about phones, but my husband sends iMessages from his ipad using the Mike....he speaks and the typing appears on the iPad.
My offspring receive the messages on their mobile phones.
If he has to use his mobile he uses a stylus and that helps a bit.
We both find the iPad invaluable and it has almost replaced the computer and the mobile phone.
A reconditioned mini iPad costs about £200 and there is no running cost at all, as long as you only use it in free wifi places.
Saves us a fortune when travelling abroad..no cost at all to keep in touch with home, read the papers, emails, BBC news etc...can phone home and see and be seen ( facetime) or just use as a phone(viber).
Hope someone will offer more help with the phone problem.