They have been calling me every day at 11;30am and it is very annoying. I too have a mortgage through Nationstar which was recently taken over from GMAC.
I have never been late on my mortgage and I always send a little extra to put towards the princpal each month. I never answer the call because I am at work but I hear the phone vibrating in my purse and it very distracting.
This # DOES belong to NATIONSTAR MORTGAGE - www.nationstarmtg.com. Their main toll free # is 888-480-2432 but it's sometimes easier to reach them by calling their collections telephone #: 888-850-9344 (they want their money, so someone ALWAYS answers quickly in the collections department!) I have my mortgage through them and they ar a pain in the [***]. I cannot wait to refinance with another company, which hopefully will have better customer service (wishful thinking???). I just told the guy at Nationstar that if I continue to have problems with phone calls (this is the 3rd or 4th time) I will just give them false contact info.