Spanish international changing into Spanish traditional

I would like to know how to prevent Word to switch from Spanish International
to Spanish traditional within the same document (even the same sentence)!!
It is very important as the autocorrections (Tools, etc.) only work with Sp.
Intl., which of course I have selected, previously. I have also selected
Sp.Intl. as the keyboard language.
I would be very thankful if you could answer my question or refer to
somebody who could.
Cristina

P.S. The language of the interface has nothing to do with it. I’ve been
using Word in English, in Spanish, and now in French.