When do you get personal business done when you work full time?

I got in trouble by my manager a couple days ago for making personal calls (on my cell phone, not office phone) during office hours. I understand that they have a right to not let me do that, but its not like I spend all day on the phone, and I don't make calls every single day.

They have told me before that its ok if I do this, but when my supervisor got onto me, she said I was taking advantage of this privilege and that if it continued then the privilege might be taken away. I recently was in the process of buying a house, so I had to talk to lenders, real estate agents, and my wife. So I probably have been making more calls than normal, but I always make sure to do it during my lunch break. That's been over with by about a month though.

I just don't understand how I'm expected to ever take care of personal business if I don't do it at work during my lunch break. I work from 8 - 5, and most of the places I would need to call are only open from 8 - 5 as well, so its not like I can call when I get home.

I'd also like to add that I just graduated from college a year ago and this is my first job in the real world, so I don't have any prior experience in this issue.