In the beginning of the film "Bug" we can observe how Agness is plagued by silent calls, that she believes were made by her ex-spouse Jerry. Originally I thought it was Peter, who is kind of crazy paranoiac, so it was part of his reconnaissance of Agnes before revealing himself. However later on we can see that Peter himself answered another silent call, so it should be someone else.
I don't think it was Jerry (it seems to me that this character tends to express himself whenever possible rather than making silent calls), so I can't see any obvious answer here. Who could that be? What these calls were supposed for in the film at all?