They call several times a day and not always under this number. It is a call from NCO Financial and they are debt collectors. You can find a lot of complaints about their practices by doing a search on NCO Financial.
The caller ID reads "TELE RESPONSE C". My parents get calls from this number on occasion, claiming to be "one of their charities". They are not in debt to anyone so there would be no reason for the phone calls. Looks like deceptive business practices to me on NCO Financial's part.