I don't get calls at night, but do get calls where my Sim gets the agitated expression and then hangs up. Due to an opportunity that they declined.
There are some that I just ignore. You can turn off the ringer, by going into the phone settings and select silence phone, but I don't think you can stop all the phone calls.
However, you can suppress Opportunities by going to Options > Game Options tab and check Suppress Opportunities. Not sure what this fully does. As I don't have it checked.
There is a Phone/Opportunity bug related to Into The Future that is fixed with a mod called Opportunity phone call fix. But I don't think it does opportunity calls at night.
If the calls are from a random Sim calling to confess attraction, you can try using a mod called More/Less Attraction Calls & Love Letters to stop the attraction calls.
