I would expect speech therapists to want to pay for the app, speech therapy apps and apps for doctors in the states are usually pretty pricey.

I wouldn't expect any medical office to balk at $9/mo . . . if anything you should raise the price, that seems too inexpensive. I'd do three plans $49, $99 and $199 depending on features/levels you can offer or maybe per doctor/staff/patient depending on your app.

Do you have Hipaa style privacy laws regarding electronic medical records in Brazil? That usually commands a premium here so same app for non-medical $99/mo for medical $199/mo.

https://www.appointmentreminder.org/pricing

I think you're pricing too low, if it provides value speech therapists are going to expect to pay for it.

Good luck, let us know how it goes.