If your mortgage payment is due on the 1st, then on the 2nd it is considered late. You should make your payment on or before the due date. As far as the company being able to call you, there are regulations set forth by the Federal Trade Commission as to collection practices. To see if they are violating this, go to:
If they are violating your rights, you can report them to the Federal Trade Commission. You can (I had to do this with a credit card I had through a store that I fell behind on) send a letter in writing to the company requesting a "cease and desist all telephone communications", and they have to comply. They would only then be allowed to contact you by mail, or e-mail. I had this credit card company calling me 3 and 4 times a day for a payment that was 10 days late. I was about 19 years old at the time, but the rules have not changed. They CANNOT call you if you do not want to be called. They do have the right to contact you though. Go to that site, see what your rights are.
Hope this helps!!
I am an Investor/Buyer/Lic. Mortgage Broker