How does one call a Portugese number while in Portugal using my own phone?
Thanks,
Assuming you already have the RS Portugal book, look in the last chapter under practicalities.
Add +351 in front of the local number.
The + sign signals the phone to figure out on it's own the necessary international dialing code (or not) to drop an initial zero (or not), etc. See also https://www.ricksteves.com/travel-tips/phones-tech/call-uk-europe.