How safe it is to provide your number online for education enquiries, etc.?

I am really concerned because I just entered my phone nubmer while enquiring for University of Phoenix Education programs and now they have my number. Do you think they will have my number on their records forever now? I spoke to two Admissions guys and both of them were really rude. So I decided to not enroll into that University for the better. But now I am concerned about them having my nubmer and mailing address. Is there anyway I can do something so that they don't have my information anymore and don't mail me stuff?