Well, that adds a whole new dimension to the saga. If you put 30 days, then give them 30 days before you call or you look desperate.
Personally when I get a bill from a vendor, I enter the due date into my Google calendar as a reminder and then send a check 5 days before it’s due. She might have done something similar and then couldn’t understand why you were calling her.
When I bill a residential customer the invoice says due on receipt (now), I give them 10 days from the date I billed them and start calling.
