Mortgage service center and this number is PHH mortgage. Your the idiot here. This number is calling you, that simply means you late on a mortgage payment and/or you have a reissued telephone number that belonged to someone that is behind on their mortgage.
PHH Mortgage Services is the servicing company which REPRESENTS AND WORKS FOR various banks with regard to mortgage accounts, HAMP (Home Affordability Mortgage Program), collection of mortgage payments and Loss Mitigation Department which deal directly with their customers' accounts, applications, processing and approval of home assistant programs. Unless you are advised by an attorney not to answer or speak with PHH, it would be wise to speak with them if you have a mortgage account with them. It doesn't get any better by ignoring situations. :)