"Afterward, I was no longer speaking to them."
Translation:Après, je ne leur parlais plus.
Usually, you need "eux" if the preposition is not "à": avec eux, pour eux, avant eux...
You still need "eux" with "à" in specific constructions: ce chien est à eux (possessive)
But if the verb is naturally constructed with the preposition "à", you use the pronoun in its indirect form and place it before the verb: il leur parle. ("il parle à eux" is incorrect)