Not necessarily personal "
a"s.
Voy a pagar al hombre (better "
le voy a pagar al hombre") = I'm gonna pay him
Voy a pagar el hombre = I'm gonna pay for him (suitable when calling an agency while organizing a bachelorette party
)
He llamado a la agencia de viajes ---> and they've answered
He llamado la agencia de viajes ---> and they've come