The Old Man was quite smart
Valak was using Bill Wilkins, the old man ghost seen tormenting the household, as a puppet to do so, but Bill was still able to send a plea for help with the two sentences that made up the statement "Help me! It won't let me go!" that had to be played simultaneously to make sense, and to give Lorraine in her vision the riddle that is the clue that leads to Valak's name to banish it.
He must've been quite smart to outwit a demonic entity like that, to be honest. Must've been quite the verbal genius in his lifetime.