Appelez-le / Téléphonez-lui

Hi Federico,

If you take a look at my answer to a similar question you will see the verbs appeler and téléphoner à quelqu'un, although they mean the same thing, grammatically use different object pronouns -

https://french.kwiziq.com/questions/view/why-il-ecrit-a-sa-tante-becomes-il-lui-ecrit

Hope this helps!