¿Cómo le dicen?
 

I hear this in Colombia. "What is your name?"
But I thought that it would be ¿Cómo lo dicen?, since decir is here a transitive verb (meaning llamar) and would take a direct object lo, rather than le (which I thought would be used in Spain but not in Latin America).

Am I missing something?

The pronoun 'le' represents an indirect object pronoun. The verb 'dicen', in this case, has two objects. What is said (by them) is the direct object. That unspoken object is the person's name. The question means, "What do they call you?"

Thanks!