Hi there Walterfromwa,
Thank you for choosing Apple Support Communities!
It sounds as though font size in apps is not able to be increased. You’re in the right place, we’d be glad to assist in seeking a solution.
First, we’d advise verifying all iOS updates are installed:
Update your iPhone, iPad, or iPod touch
If the issue continues or you are already up-to-date checkout this resource below:
Change the font size on your iPhone, iPad, and iPod touch
“You can change the size of your font in Mail, Contacts, Calendar, Phone, Notes, and other apps that support Dynamic Type.”
When changing the size of your font this change can be seen in apps that support Dynamic Type, are you seeing the size of the font change in apps such as Notes?
Keep us posted,
Cheers!