Unfortunately it is not possible to change the font of Skype on iOS.
I am sorry for the inconvenience.
If answer was helpful please give Kudos and if issue is resolved mark it with solution for other users. Thanks!
I have asked about increasing the size of the font on the chat page - and all other places - because it is far too small for efficient use. The answers you give to previous queries do not seem to address the problem. HOW DO I INCREASE FONT SIZE ON SKYPE?